One amazing feature in Stellaris game is those minor races. First they are not visible on the star map. When a science ship survey the star system it may find out that some of the planets are populated with less developed beings, like one in the stone age, medieval age, modern age or early space age. They will slowly advance, but some of them may not advance enough to become a major race during the whole game. The constructor ship can build an observation station near the populated planet, which give some additional options, like one to help the race to evolve, or infiltrate them like in those sci-fi horror movies with aliens in human form trying to seize the governments.