Each year when teaching my class about health and nutrition I always do this germ science experiment. We take 3 skinned potatoes and rub one with all of the kids hands, one we rub all over the carpet in the classroom, and the last one we take outside and roll it in the grass and dirt and gravel. Then we label our potato cups and put straws into the potatoes for handling so we don't contaminate our experiment when we check them out everyday. Then, we make a hypothesis about which potato is going to grow the most germs over the week. Every year the students hypothesis is always the potato that we rolled around outside. I think this is because it looks the dirtiest. But... I know which one actually grows the most germs! You will have to wait to find out the results or do the experiment with your class! ;-)