This cluster of stars has been known since ancient times, and was mentioned by Homer in 765 B.C.  In Greek and Roman legend they were known as The Seven Sisters or The Pleiades. Only 6 of the Seven Sisters can be seen with the unaided eye today. It is said one of the sisters has faded into the background because she is embarrassed to have married a mortal. A Kiowa Indian legend also identified this star group as a set of maidens. In that legend, they fled high into the sky from off the top of Devil's Tower in Wyoming to escape a giant bear who was after them. Sometimes this cluster is seen as a (and mistaken as the) little dipper.

The dozen or so brightest stars of the Pleiades are gigantic, young, blue hot and bright members of a much larger cluster of 400-500 gravitationally linked stars. Their intense light is lighting up and reflecting off the thin interstellar gas that resides between us and them. That gas is actually so sparse that there is less molecules of it per cubic meter than the best vacuum that could ever be created here on this earth. However, since we are looking through many light years worth of that incredibly thin gas, there is cumulatively enough to see the large interstellar structural distribution of it between the Pleiades and us.

80mm F6 AstroTech Refractor, (480mm F.L.) Modified Canon 300D camera with IR-UV filter, placed at the scopes prime focus
6 photos aligned and averaged together, then brightness, color, and contrast enhanced. Click on photo above for a full frame full rez image.
Each photo, 400 seconds exposure at ISO 800