Coloring books are printed books filled with line art illustrations that people can fill in with colors using various tools like crayons, colored pencils, or markers. They are designed for both children and adults, offering a creative outlet and a way to relax. The images can range from simple shapes to intricate designs, catering to different skill levels and interests. In recent years, coloring books have gained popularity as a form of art therapy, helping individuals reduce stress and improve focus. Many themes are available, including animals, nature, and mandalas, allowing users to choose what resonates with them.