A hair whorl is a patch of hair that grows in a circular direction around a visible center point on the scalp. They either grow clockwise or counterclockwise. How many of these we each have and in which direction they rotate depends on our genetics.
The geneticist Amar Klar even researched whether the direction a hair whorl grows determines if we are right-handed or left-handed. If the hair swirls in a clockwise direction, he found, this might suggest that the person is right-handed.