Countershading, or Thayer's law, is a method of camouflage in which an animal's coloration is darker on the top or upper side and lighter on the underside of the body. This pattern is found in many species of mammals, reptiles, birds, fish, and insects, both in predators and in prey.

Abbott Handerson Thayer was an American artist, naturalist, and teacher. As a painter of portraits, figures, animals, and landscapes, he enjoyed a certain prominence during his lifetime, and his paintings are represented in major American art collections. He is perhaps best known for his 'angel' paintings, some of which use his children as models.