The inside of a Poké Ball from the "Pokémon" anime series features a "Pokémon-friendly" environment designed for the comfort of a particular Pokémon. The ball contains mirrors and circuitry inside the device, and a Poké Ball converts a Pokémon from matter to energy and then stores the creature inside a baseball-sized ball.
Poké Balls shrink to the size of a ping pong ball once a Pokémon is caught for easier storage inside a trainer's backpack. Trainers push a button on the Poké Ball to change its size. Most Pokémon remain in their storage containers until the trainer lets them out. Although the inside of a Poké Ball has never been fully explained, some Pokémon trainers tell the main characters about different aspects of the ball.
Normally, a Poké Ball is thrown at the creature, and then it is either captured or it escapes. If a Pokémon refuses to be captured the first time, a trainer can throw it again to try to capture the creature again. Some Pokémon are able to escape from their Poké Balls at will even after their capture.
In the fictional anime, Poké Balls have been around for centuries. There are 26 different Poké Balls, each with different aspects designed to catch certain types of Pokémon.