I gave the girls food coloring to add to water in little paper cups. They enjoyed mixing it up.
The next day, I asked the kids to make some predictions about what happened, and then observe the results. When we cut through the celery stalk, we could clearly see how the colored water was pulled upward through the thin tubes. This Spring we'll be repeating the experiment using white Carnations to see if we can get the flowers to change color. I love when science doesn't have to involve a lot of preparation and complexity - this is an easy fun experiment that little ones love..
UPDATE: I was so inspired by how much my kids enjoyed early learning games that I created the La La Logic Critical Thinking Curriculum for 3-6 year olds, which includes online brain challenge games, printable worksheets, enrichment activities and more!