Steven gently holds Toady as Claudia examines the croaking toad with a magnifying lens.

With his teacher sitting nearby to offer encouragement, Eric plants a seedling he grew at home from a grapefruit seed.

Brittany caresses Bunny, while Fred listens intently to hear the rabbit's heartbeat.

What do these five preschoolers have in common nature. They're all observing nature in action, exploring living things and learning basic scientific concepts through spontaneous play. Young children are scientists by nature. They are born with a strong sense of curiosity that impels them to explore, experi- ment, and make discoveries. Both the 4-year-old preschooler who compares her handprints with her friend's and the 34-year-old biologist who com- pares various gene combinations in a lab share a basic human desire to find out now things work and to make sense of their world. This is the foundation of all scientific thinking.

Look around and you will see that science is everywhere — in our rooms, on our playgrounds, in our lunch boxes, and within each individual. As teachers, we need to create an environment in which this natural thirst for knowledge is nurtured.

Science learning takes time. Children need to have a large block of time each day in which they are free to follow their curiosity and experiment with materials to find for themselves the answers to questions as, "What will happen if ...?" and "How will it change?" They also need time to test their results, often by repeating the same experiment again and again. A child may return to the same type of experiment over a period of days or even weeks, if he or she is working on a complicated theory or project that evolves slowly, such as growing plants, making raisins from grapes, or watching the metamorphosis of a butterfly or a frog.

Science learning requires adequate space. Children need enough room to move about freely and actively explore the wonders of the natural world. Science learning also requires the right types of space. Some science exper- iments are messy, and they need a place in which drips and spills won't be a problem. Others are noisy, and they need a place in which the noise won't interfere with other children's needs. Many science experiments require sun- light or involve weather, so windows or adequate outdoor spaces are important.

An environment filled with real hands-on materials for exploration will stimulate children's curiosity and provide them with opportunities for discovery. A room for young children is not a place for quiet sit-down, paper-and-pencil tasks on worksheets and workbook pages. Instead, it's a laboratory of learning about the real world through interactions with people, plants, animals, and materials.

While science can happen anywhere, a discovery, or science, center is the place where plants are grown, observed, and recorded; where rocks are collected, examined, broken, and grouped; where nuts are cracked, tasted, and sorted. Because the discovery center plays a major role in learning, it needs to be well thought out and planned. It's not enough to place a few rocks, a magnifying glass, pinecones, and nuts on a tray and call it the discovery center. The discovery center should offer chil dren many opportunities to explore, experiment, think, and, of course, discover.

It's also a place to provide a variety of science activities from which children can choose. A good rule of thumb for a smooth-running center is to have approximately two and a half activities per child using the center. For example, if four children can use the center at one time, provide 10 choices for them. Too many activities may cause frustration — "I'll never do them all"— and too few activities can create anxiety — "I'll never get a turn." Change the activities when children give you signals that they're bored with them, such as ignoring the materials or repeatedly using them in inappropriate ways. This might happen after a month or after a day, depending on children's interest.

The successful discovery center is child-directed. A good way to accomplish this is to include rebus (picture) directions for each activity that's in the center. This is especially helpful for those children who don't speak English. Rebus directions allow children to choose an activity that interests them, do the activity, return it to its place, and then choose another activity — without waiting for verbal directions from you. (Of course, if they have trouble, they should feel free to come to you for help.)

It's also important for you to organize the discovery center in a way that helps control the use of equipment and makes cleanup easy. When you do this, the discovery center offers indirect guidance for the children working there. Put the activities on low shelves so children can choose them independently. Also, make each activity self- contained. Place them on trays, in buckets, or in baskets. This way, you define the boundary of the activity and give children a place to return materials. Plan for easy cleanup by keeping a trash can, sponge, whisk broom, or any other item that is needed nearby, within easy reach of children.

Perhaps the most important ingredient in a room for science learning is the emotional climate that you create. In a supportive environment, children are encouraged to touch, to investigate, and to find out for themselves the answers to their questions. They're encouraged to take risks, without the fear of "getting it wrong." Their ques- tions and ideas are treated with respect, and their explo- rations are validated by your interest. When you help chil- dren make their own discoveries — and share with them your own natural sense of wonder, curiosity, and joy of discovery — you're creating an environment in which genuine learning can take place naturally and sponta- neously throughout each and every day.

One of the best things about encouraging young childrens explorations is that you don't have to be a science expert yourself to do a good job. It's not important that you know a lot of scientific terminology or that you understand all the underlying scientific principles for the way things work. That kind of information will come at a later stage of education. When working with young children, your role is not to serve as a dispenser of knowledge, but as a facilitator of learning. In fact, if you don't know the answer to a child's question, discuss howyou can go about getting the information you need. Learning how to find out, and that it's okay not to know all the answers, is more important than a quick response. When you provide the time, space, materials, and emotional climate for children to follow their natural curiosity and sense of wonder, you're building foundations for lifelong scientific thinking.

With so many choices and opportunities for learning, deciding what to put in the various learning centers may, at times, seem confusing. It helps to think about the ways young children learn. As you know, they don't separate their learning experiences into fragmented subject areas, such as "language" or "problem solving" experience a young child has affects the way he or she approaches other experiences. Their learning is Integrated, with one idea flowing into another in a natural, spontaneus way.

Keeping this natural integration in mind, consider organizing materials and planning experiences for learning within the framework of thematic units. When you use themes to pull your curriculum together, you provide a foundation for learning in all areas. Every activity in every learning center becomes meaningful to children and relevant to the topic being explored. Within a thematic unit, children who choose to build with blocks, paint at the easel, look at picture books, or work with puzzles are all experiencing activities related to a central topic that sparks their interest. Their learning environment makes sense to children because all the activities work together.

How do you go about selecting themes? Listen carefully to children's conversations. Pay attention to interests, questions, and ideas children express. One idea will lead to another, as you and the children enter into a partnership and go about planning meaningful learning experiences.

Let's take a look at the way one class developed a thematic unit from a lunchtime conversation.

One day at lunchtime, as Susan was sipping milk through a straw, a curious expression appeared on her face. She turned to the boy sitting next to her and asked, "Kevin, where does the milk in these little boxes come from?" Without a moment's thought thought, Kevin answered, "From all the big boxes!" LaTron jumped into the conversation and said, "No, it doesn't. It comes from the store!" Then Maria chimed in, "My milk comes from the refrigerator." As their teacher, Ms. Young, listened to the children's conversation, it became clear that this would be a good time to study milk.

The next day at group time, Ms. Young encouraged the children to discuss where they thought milk comes from. She wrote all their ideas on an experience chart, but the children still had questions about milk and its source. Ms. Young suggested that they do research, and the children decided to ask their families where milk comes from.

Without being aware of it, the children were following the scientific method. They identified the question, "Where does milk come from?" and wrote their hypothe- ses on the experience chart. Now the research phase was beginning. The children were encouraged to talk to their families about milk and to bring in from home any books about the subject.

The next morning, the children were excited to share what they'd learned. They all agreed that milk comes from a cow, but that answer only raised other questions. How does the milk get in the cow? How does the milk get out of the cow? How does it get in the boxes? Why is it white? How does it get to the stores? Are there different kinds of milk? Ms. Young and the children discussed ways to find out more about cows. They decided a trip to a dairy farm would be the best way, but since there wasn't one in their area, they opted to watch a video or movie about cows and milk.

The group followed through on their plan, an important step in research, and watched a video that took place on a farm and showed farmers and machines milking cows. Again, many questions were answered, but new ones appeared. For example, when they saw a goat being milked, it caused quite a stir. The children had been sure they knew exactly where milk comes from! Goats? It was an exciting discovery. The children were curious about the different tastes of cow and goat milk. They decided to have a tasting party and to serve only milk and foods made from milk. The children were making plans to use their senses to gather knowledge.

During the following week, the children's interest remained strong and they continued to gather information on the subject and reformulate their ideas. The library center was filled with the books about cows, farms, and milk that the children brought in from home. Ms. Young also provided blank-paper books, and some of the children created their own "cow books," which they read to friends, sharing their new ideas and information. Other children looked through the book The Cow Who Fell In the Canal by Phyllis Krasilovsky (Doubleday), while they listened to the accompanying tape.

In the block corner, two groups of children worked on different projects, while one child played alone. In one group, three children were trying to duplicate a barn they'd seen in a book. There were intense discussions about where to place each block in order to make the barn walls stand. Nearby, two other children were playing with plastic farm animals. They had built four fenced-in living areas with the blocks, and they were deciding which animals to put in each. Without being aware of it, they were grouping the animals, a very basic and necessary scientific skill. Carlos, who was working alone, built a large fenced-in area for one cow. Mrs. Rojas, the assistant teacher, stopped by and asked Carlos to tell her about the cow and the area he had constructed. He carefully explained, "My cow has to make lots of milk, so it has to eat lots of grass, so it needs lots of ground for eating lots of foods." After watching the video about cows on a farm, Carlos had fig- ured out that if his cow eats more, it can give more milk.

In the art center, Ms. Young had placed black, brown, and white paint at the easel. Offering more neutral colors was an invitation for children to experiment with cowlike colors, while those children who were ready for representational art could attempt to create a cow.

In the manipulative center, two children were hunched over a puzzle of a cow, trying to find the various body parts to put in the right places. Two other children were trying to match pictures of baby animals to their mothers, which helped them become aware of similarities and differences in the animals. Another child was putting a set of picture cards, which showed the different steps involved in milking a cow, in sequential order.

The children had heard cowbells in the video, and this led to a discussion about bells. Following their interest in the sounds they'd heard, Ms. Young added different-sized cowbells to the music center for free exploration and experimentation. As a few children compared the different pitches and tones, the teacher took advantage of their interest and asked, "What do you think makes the bells sound different? What makes them sound the same?" This was a perfect opportunity to combine music with science.

In the dramatic-play center, several children were pretending to farm the ground, using the buckets, rakes, and shovels that Ms. Young had added. They also played with the different milk and milk-product containers and packages that the teacher provided. When Jacquelyn held up a yogurt container and said, "My mommy eats this every morning for breakfast," the children decided to add yogurt to their tasting party.

Ms. Young and the children got out the party list and added yogurt to it. After some discussion, they also added cottage cheese, cheese, whipped cream, skim milk, and sour cream to their list. And although they all agreed they knew what chocolate milk tasted like, they decided it would be fun to have it at their party, anyway. The list was growing.

A lively and interesting discussion arose about buttermilk. When one child said he hated it's taste, others agreed to leave it off the list. But when Ms. Young asked the group how many children had actually tasted it, no one else had. The teacher decided this was an excellent time to make butter with the children, so they could discover what but termilk was and where it came from.

The next day in the science center, Ms. Young set up a butter-making activity. On a tray were small baby-food jars with lids, heavy cream, a tablespoon, a package of crackers, cups, and a rebus recipe card to show the children the steps in making better. Kevin and Susan, the two children who began the cow/milk study, chose to do the activity first. They each put a tablespoon of heavy cream into a jar and put on the lid. Then they shook and shook their jars, stopping frequently to observe what was happening. Mrs. Rojas encouraged them to continue shaking the jars. After a while, Kevin shouted, "Look! Look! I see Kevin's butter. Then Susan discovered butter in her jar. Her lump of butter was much larger than Kevin's, and the admiration from the group started all over again.

Kevin's and Susan's discoveries inspired the others in the class to make their own butter, which they spread on crackers to taste. As the children made the butter, they poured off the liquid into a large, clear jar. No one seemed to notice the jar filling up until one child said, "What is that stuff? It looks yucky!" This drew some of the other children into a discussion about the liquid. Mrs. Rojas listened to see if they would guess that this was buttermilk. After a while, she asked, "What does it look like? What else do you know that is the same color?" LaTron solved the problem. "It's buttermilk!" she shouted. "Yuck!"

The two teachers knew that tasting it would give the children more information about the liquid, but they refrained from suggesting a trial by such unwilling taste buds. Instead, Ms. Young began a discussion of how people know whether they like the way something tastes. Finally, the group agreed that the only way to know if they liked the taste of buttermilk was to taste it. A bit of butter milk was poured into a small cup for each child. Reluctantly, children took very small tastes — and they unanimously decided that they didn't like it. But they did agree that by tasting it, their decision was scientifically valid because it was based on research.

Finally, it was time for the tasting party. The children reviewed their list of foods. It had grown quite a lot since they first decided to taste the difference between cow and goat milk. With Ms. Young's help, they assigned foods to bring in from home and volunteered for different jobs. The room was filled with excitement the day of the party. The children cut up those foods that needed it, filled cups with small scoops of the other items, and set the table.

Then the actual taste-testing began. Each item was sampled and discussed. The air was filled with joyful discoveries as the group shared their different ideas and opinions on the merits of the various foods.

When the children had tasted everything and cleaned up from their party, Ms. Young pulled out a large sheet of paper made into a bar graph. On each line she had drawn a picture of one of the foods the children had tasted. She asked them to think about which one they liked best. As each child shared which food he or she liked best, the teacher drew a stick figure of the child, with his name beneath it, beside the picture of the food. Then they examined the results of their taste-testing. They compared the best liked — chocolate milk — to the least liked, which had zero votes — skim milk and cottage cheese. Ms. Young made smaller copies of the graph so each child could take one home and share the results of the taste-testing party with his family. The original graph was placed on the wall at children's eye level for them to examine at their leisure.

To bring closure to the milk study, the children decided to make a big book about milk. Each child contributed to it by drawing a picture, dictating a story, or doing both. The book was assembled using notebook rings and placed in the library center, where children could look at it when they pleased. The children felt satisfied and delighted with all the new information they had learned about cows and milk.

These teachers introduced new ideas to the children in ways that made the study about milk and cows meaningful. Offering experiences based on a theme the children chose helped them leam about their world, organize information, and structure their thinking. They truly learned about cows and milk because they made discoveries on their own, rather than having the information "taught" to them. Although the teachers focused the activities on one topic, the children were encouraged to follow their interests — whether by writing a story, working a puzzle, ringing the bells, painting at an easel, or building with blocks. These learning areas may not traditionally be labeled science, yet they allowed the children to fol- low their curiosity and explore a variety of scientific concepts.