Before we talk about what we put on our hair, let’s understand the hair itself.

We’ll explore the strand, the scalp, and what happens when hair meets water, heat, styling and everyday care.

One topic at a time, in plain language—with room for the differences that make your hair your own.

You don’t need to become a scientist to understand your hair. But understanding the science can help you ask better questions and make more informed choices.

Our first lesson: the hair shaft.