There are two things about the Hubble Space Telescope that make it stand out and justify giving it a chapter to itself. The first is that when it was launched, it became the most scientifically productive single instrument ever made, with well over 15,000 scientific papers being produced in 20 years. The second is that this is as near as we can ever get to a time machine. By looking at the faint galaxies at immense distances, we are looking further back in time than we have ever been able to before, towards the beginning of the universe.