To the left, we show a picture of the Bullet Cluster, which provides some of the best evidence for dark matter. The pink areas correspond to areas where we find visible matter. Due to its enormous mass, the Bullet Cluster bends space; thus, it generates gravitational lensing effects. Studying these effects allows us to determine where most of the mass is located. This corresponds to the blue areas. Thus, although we can only see the matter in the pink areas, most of the matter is in the blue areas; since this matter is invisible, and we call it “dark matter”.