Molecules A and B meet, marry, and beget the species. This takes place in one-millionth of a billionth of a second. This is a fundamental process in nature, and the world was looking for a way to be able to see the process. But many brilliant people said it couldn't be done.
Once we understand how molecules are formed, we can manipulate them. If you can manipulate molecules, you can manipulate genes and matter, you can synthesize new material - the implications are just unbelievable.