Messier 45, also known as the Pleiades or the Seven Sisters, is an open star cluster located in the constellation Taurus. It is one of the nearest star clusters to Earth, at a distance of about 444 light-years. The cluster contains several hundred stars, with the brightest ones easily visible to the naked eye. The Pleiades is famous for its blue reflection nebulae, which are clouds of dust and gas that scatter light from the stars. The cluster is thought to be relatively young, with an estimated age of around 100 million years. It has been a significant object in various cultures and is often associated with mythology.