Why Teenage Brains Are So Hard to Understand

The following story is excerpted from TIME's special edition, The Science of Childhood, which is available in stores, at the TIME Shop and at Amazon.

When Frances Jensen’s eldest son, Andrew, reached high school, he underwent a transformation. Frances’s calm, predictable child changed his hair color from brown to black and started wearing bolder clothing. It felt as if he turned into an angst-filled teenager overnight.