A "squirrel cage" is a type of exercise wheel designed for small animals, particularly rodents like squirrels and hamsters. It allows them to run and play while staying in one place, providing both physical exercise and mental stimulation. The wheel is typically made of a circular frame with a solid or mesh surface that spins around a central axis. In addition to being a fun toy for pets, squirrel cages are also used in various scientific experiments. They help researchers study animal behavior, exercise patterns, and even the effects of different environments on small mammals. Overall, squirrel cages serve both recreational and educational purposes.