A coloring book is a book filled with black-and-white pictures that you fill in with crayons, colored pencils, or markers. Each page shows an outlined drawing, like a dinosaur, a castle, or a garden scene, waiting for you to decide what colors to use.

Coloring books have been popular since the early 1900s, when publishers first realized that kids enjoyed bringing printed pictures to life with their own color choices. Today, you'll find coloring books about everything: animals, superheroes, vehicles, geometric patterns, even famous paintings simplified for coloring.

While coloring books are especially popular with younger children learning to control their hand movements and explore colors, many adults enjoy them too. The focused, creative activity can be relaxing after a stressful day. Some coloring books feature intricate designs specifically meant for older kids and adults.

The phrase coloring book is sometimes used to describe things that are overly simple or childish. If someone dismisses a movie as having a “coloring book plot,” they mean it's too predictable and uncomplicated. But there's nothing wrong with the real thing: choosing colors, staying inside (or outside) the lines, and making creative decisions about how a picture should look.