Plant some bean seeds in a small pot. Your child can plant, water, and measure the bean as it grows. Beans are ideal because they grow very quickly.

Plant some seeds around the outside of a clear plastic or glass pot, so you can watch them sprout. First line the pot with a piece of paper towel, then put the soil into the pot. Slip the bean seeds between the paper towel and the side of the pot and they will be easy to see. Put the seeds in various positions (i.e., on end, rounded side up, rounded side down). Water and watch as the roots all go down and the stem goes up, no matter how the seeds are placed.