Sam was an avid eater of greasy, cheesy pizza until her early 20s. Now, dairy has her running to the bathroom (tmi). Why is that the case for so many people all over the world? This week’s episode covers what causes lactose intolerance, why it’s not the same thing as a dairy allergy, and what might have caused a rapid shift in humans’ ability to digest lactose. Links to the Tiny Show & Tell stories here and here. Episode transcripts at acs.org/tinymatters