I get asked this a lot, “why is some people hair curly?”. The shape depends on the shape of the hair follicle. This tiny structure guides the hair fiber up a sort of tube as it grows. The inside of the tube determines if the hair is curly or straight — ovals produce curly hair and circular tubes yield straight hair. If you think about gift wrapping ribbon, when you try to make it curly, you take the scissors and you pull it on one side, so you kind of flatten the one side and it curls. So you’re changing the shape of one side compared to the other. When it’s oval, one side is curved and the other side is flat, which makes it curl.