Some Pokemon evolutions include Ivysaur evolving into Venusaur, Meowth evolving into Persian and Ponyta evolving into Rapidash. Evolution is a key element of the Pokemon games, and players must to figure out how to make a Pokemon evolve.
Not all Pokemon evolve in the same way. Some Pokemon evolve after they level up and become stronger. This is the case for Meowth, who evolves into Persian at level 28. Other times, Pokemon players have to trade Pokemon to make them evolve. For example, they have to trade Kadabra to make him evolve into Alakazm.
Pokemon also evolve when they come into contact with certain stones. For example, Poliwhirl evolves into Poliwrath after coming into contact with a water stone. Another example is Growlithe evolving into Arcanie after touching a fire stone. Sometimes different stones have different effects on Pokemon. For instance, the Pokemon Eevee transforms into Flareon if he comes into contact with a fire stone, Jolteon if it's a thunder stone and Vaporeon with a water stone.
Happiness evolution first came about with "Pokemon Gold" and "Pokemon Silver." For example, Pichu evolves into Pikachu after his happiness reaches a certain level. Some Pokemon only evolve depending on the time of day it is. Evee has two happiness forms. If Evee evolves from happiness at night, he transforms into Umbreon. If it happens during the day, he turns into Espeon.