I love science, it's was always my favorite subject in school. I even majored in biology in college. Luckily my daughter seems to have inherited my love of science. She loves learning about insects, dinosaurs, space, geology, and this year she asked to learn about germs. And so we've spent the last few months growing bacteria on agar in petri dishes and testing all sorts of products. One of our experiments tested the effectiveness of various natural household cleaning products. If you haven't already, you can read about it here . Since our essential oil spray scored the worst on our previous experiment, we were curious if essential oils would work better full strength and which ones kill germs best, so we designed an experiment to find out. Our Experiment: Which Essential Oils Kill Germs Best? First we decided which essential oils to test. We went with tea tree, cypress, eucalyptus, clove, lemongrass, and sweet orange and then I had my daughter write a hypothe