Just about everyone will agree that trees are made from sunlight, water, and soil the trees suck up from their roots. But the surprising truth is that trees are made from air! Trees are solar-powered machines that convert air into wood. Why is it that, despite the fact that photosynthesis is one of the most widely taught subjects in science, so few people really understand the central idea underlying this system? Starting with this question, program two explores why something taught in school can go unlearned and shows that we often teach without regard to what children actually need to know.