You may have heard someone say, "My desk has become a black hole!" You may have seen an astronomy program on television or read a magazine article on black holes. These exotic objects have captured our imagination ever since they were predicted by Einstein's Theory of General Relativity in 1915.

Photo courtesy NASA/Space Telescope Science Institute (J. Gitlin, artist)
Artist concept of the near vicinity of the black hole at the core of galaxy NGC 4261

What are black holes? Do they really exist? How can we find them? In this edition of HowStuffWorks, we will examine black holes and answer all of these questions!