Micah was an Ephraimite who was the founder of the idolatry and false priesthood of the Tribe of Dan. Micah lived during a period of time where there was no King, nor Judge over Israel to keep the people in line with God's commands. Micah started a false deviation of the true worship of God by creating idols and establishing a priesthood in his house. Originally, this idolatry and priesthood was intended for him and his family (specifically his mother), but the Danites stole his family idols and took the high priest with him to the City of Dan.
Micah is recorded in the Book of Judges and is documented as an example of Israel's disobedience to God without the rulership of a King. Despite his idolatry and apostasy, Micah was very hospitable to Israelites traveling through Ephraim.
Micah was born and grew up in the hilly tribal lands of Ephraim. He lived during a time where Israel had neither King nor Judge, so there was great immortality in the country. Micah and his family worshipped Yahweh; however, were susceptible to imitating the idol creation of the Canaanites. Micah had a shrine in his home at one point. Details about his father are unknown and very little is known about his mother.
At one point his mother acquired a wealthy sum of eleven-hundred pieces of silver. His mother swore a curse by God's name to punish anyone who would steal her silver. His mother's curse was repeated to Micah.
Micah's Household Idols
For one reason or another, Micah stole his mother's silver fortune. Once his mother discovered her silver had been stolen, he returned it and admitted to his thievery. His mother blessed him for returning the silver and did what she thought was "honoring" to God with the silver. Two hundred pieces of silver were sento a smith and were crafted into an image; an action that Micah's mother thought was dedicated to God, even though it was in direct contradiction to God's commands. This demonstrated the evil of Israel without proper rulership to keep the people accountable to God.
Micah placed his mother's idol in his house on his shrine. He created an ephod and some figurine gods. Micah appointed one of his sons to be the priest over his personal household "worship" of God. 
Some time later, Micah encountered a Levite named Jonathan (the son of Gershom and grandson of Moses) at his house. Jonathan was seeking a place to reside and so Micah offered him residence in his own house, in exchange for his services as a priest. Micah treated Jonathan like one of his own sons. After gaining Jonathan as a priest, Micah believed he had God's favor over his idolatry.
Dan Steals His Idols