Open star clusters are groups of stars that are loosely bound by gravity and typically contain a few dozen to a few thousand stars. These clusters usually form from the same giant molecular cloud and are relatively young, often just a few million years old. They can be found in the Milky Way and other galaxies, and their stars are often spread out over a larger area compared to more tightly packed clusters. Unlike globular clusters, which are older and more densely packed, open star clusters can disperse over time as their stars drift apart. They are often associated with regions of active star formation and can contain a mix of different types of stars, including hot, bright stars and cooler, dimmer ones. Examples of well-known open star clusters include the Pleiades and Hyades.