There are little bugs on foods called "germs" or "bacteria" that could make us sick. They are everywhere, on food and even on your skin. The one on your skin are not bad for but the ones on food CAN be bad. That's why we cook our food so all the bugs die. The bugs die but the poop they leave behind are still left behind. The poop is too small to see but that is what makes you sick. Even if all the bugs are gone, the poop is still there.