Curl and Frizz
In an ideal environment hair is a cylindrical structure made up of several elements. However, we live in a world that contains many external factors that make hairs change their shape. One of the main and most noticeable shapes that we recognize hair by is an irregular structure change known as frizziness or curliness. This phenomenon is caused by many factors including static hair charges, intrinsic hair memory, humidity, and other natural events.
Our hair can absorb a lot of moisture and cuticles can swell significantly when humidity is encountered. Because water vapor is scattered in a non-uniform manner through space some parts of hair strands become swelled significantly more than others. Swelling expand hairs differently in different places thus causing it to bend, curl, and frizz.