Explain to the children that we will be putting celery stalks into water. Then we will be adding food coloring to the water. I used two different vases with two different colors. Have them come up with a hypothesis about what will happen to the celery after adding food coloring to the water. Have them draw the celery every day and record how it changes for four days. On the last day have them review their hypothesis to see if it was correct or not.