The spiral galaxy M33, also known as the Triangulum Galaxy, is one of our closest cosmic neighbors, just three million light-years away. Home to some forty billion stars, it is the third largest in the Local Group of galaxies after the Andromeda Galaxy (M31) and our own Milky Way. M33 is popular with astrophotographers and from exceptionally dark sites it can even be seen with the naked eye. This image shows M33 in far-infrared light, revealing the glow of cosmic dust in the interstellar medium that permeates the galaxy. The patchy, disorganised structure of M33's spiral arms resembles a tuft of wool, leading astronomers to classify it as a flocculent spiral galaxy. The brightest spots sprinkled along the spiral arms are dense pockets of gas and dust where massive stars are born. The most prominent of these is NGC604, visible in the upper left spiral arm. This is an enormous star-forming region where hundreds of thousands of stars are taking shape.