This famous double cluster was already known in antique times and was first cataloged by the Greek astronomer Hipparchus in 130 B.C.
Both clusters are visible with the unaided eye between the constellations of Perseus and Cassiopeia as a somewhat bright patch vaguely resembling the number 8.

The clusters are at a distance of 7.100 & 7.400 light years and are physically close, being only a few hundred light years apart.