WHO?
Who: A man by the name of Edwin P. Hubble discovered other galaxies in the universe, the first being Andromeda. This made scientists know that our galaxy wasn’t the entire universe, and there were other galaxies around us. This paved the way for astronomic research in the future, which is what is known today. Scientists are still discovering more about the universe and what's in it today, and there will always be more to discover.