Stars are constantly moving through the Universe just like everything else. As they move, their gravity effects the stars nearby. Slowly they come together and form galaxies. Some are made up of tens of millions of stars working together. What is truly amazing is that they form the same shapes.
Astronomers think that the elliptical galaxies are older than the spiral ones.
This is the M100 spiral galaxy. You can see more pictures of galaxies at WWW.NASA.GOV . Andrew Rader Studios, All rights reserved.