Find out what preschoolers currently know about day and night. Ask questions about what happens during the day and night, and what makes them different. Write down their ideas and have them draw pictures depicting day and night.

Plant grass seeds in two small paper cups with soil. Have the preschooler water the seeds and place one cup in a window and the other in a dark place. Each day, have the child check the progress of the growth of the grass in each cup. Discuss the importance of the sun in helping the grass grow.

Read a book about nocturnal animals, such as "Creatures of the Night" by Stephen Brooks or "Good Night Gorilla" by Peggy Rathmann. Any book about bats, raccoons, owls or foxes would also be appropriate. Print out or draw pictures of both nocturnal and diurnal animals animals. Create a chart with a column for day and one for night. Have preschoolers separate the animals based on when the animals are awake and active. Use Velcro circles to move the animals around on the chart.

Have children make white marks on a piece of black paper to make stars. Using a yellow watercolor paint, have children brush paint over the paper. The white stars will stand out, as the crayon wax resists the paint. Discuss how the sky looks different at night than during the day. Read books about the moon including "Goodnight Moon" by Margaret Wise Brown.

Create a scavenger hunt for preschoolers using items that are associated with morning routines and nighttime routines. Use empty boxes of cereal, a photo of a school bus, a sunrise and birds to represent morning. Hide new toothbrushes or photos, pictures of bathtubs or tub toys, pillows, and pictures of nocturnal animals to represent night.