Mega Evolution is a mysterious process whereby a Pokémon temporarily gains power beyond its normal capabilities.
ProcessThere are three known requirements to Mega Evolve. First, the Pokémon must have a Mega Stone particular to its species (ex. the Kangaskhanite for Kangaskhan). Second, the trainer must have a Mega Ring. Third, the Pokémon and trainer must have a strong bond. Only certain species of Pokémon are known to Mega Evolve.
Once a Pokémon Mega Evolves, its power increases and it may even change type. This transformation lasts only a short while before the Pokémon returns to normal.