From Bulbapedia, the community-driven Pokémon encyclopedia.
A Scientist (Japanese: けんきゅういん Kenkyuuin, Researcher) is a type of Pokémon trainer that first debuted in the Generation I games. They are men in lab coats and glasses. They are often (but not always) aligned with Team Rocket, as shown in Generation I, Generation II, and Generation III, and with Team Galactic, as shown in Generation IV.
They generally use inorganic or artificial Pokémon such as Porygon, Muk, and Voltorb.
In the English version of Pokémon Colosseum, Scientists are known as Researchers. In Pokémon Stadium, the scientist is known as Lab Man.