Who created Mjölnir, Thor's hammer? (in Norse mythology)

Mjölnir is the hammer of Thor, the Norse god associated with thunder. Mjölnir is depicted in Norse mythology as one of the most fearsome and powerful weapons in existence, capable of leveling mountains. In his account of Norse mythology, Snorri Sturluson relates how the hammer was made by the dwarven brothers Eitri and Brokkr, and how its characteristically short handle was due to a mishap during its manufacture.