YouTuber Mark Rober got some powder with the delightful name Glo Germ, which glows when exposed to ultraviolet light. He then went to a 3rd grade classroom and put some of the powder on the hand of the teacher (the students were not told about the experiment). The teacher shook the hands of three kids. During recess Rober put more powder on the hands of a 3rd grader who agreed to allow it. Then at lunch he shined his UV flashlight on the kids and the the classroom. The dust was all over the place.