The Walking Rainbow science experiment is toddler friendly and the easiest science experiment around. Depending on the age you can teach different scientific lessons. Since Nori is so young I kept it basic by just going into detail about color mixing. She was so excited to see the paper towels turn into different colors. I also took the opportunity to introduce primary colors and secondary colors (surprisingly she "understood").
All you need are the following items:
6 cups or mason jars
Food Coloring (Red, Yellow and Blue)
Water
Paper Towels
Timer
Then follow these instructions:
Fill up the 3 glasses with water evenly to the top
Add food coloring to the cups with water (red in one cup, blue in one cup and yellow in one cup).
Roll papers towels into circular shape and put one end in the in the jar with the food coloring and the other end in the empty cup.
Next wait to see the the finished results.
(The paper towels will immediately begin to soak but it can take up to 36 hours for the process to be complete. It took us about 27 hours.)
(DISCLAIMER: NORI ADDED WATER AT THE END OF THE EXPERIMENT, I SUGGEST YOU DON'T ADD ANY ADDITIONAL WATER)