From Harvard Magazine:
The scenes are familiar from biology textbooks. A long string of DNA is copied to form a matching strand. A virus infects a cell by stealing through its membrane. Two white blood cells meet and confer before launching an immune attack. In textbooks, all these processes that are so fundamental to the lives of cells are typically depicted in drawings or static snapshots captured by powerful electron microscopes. But that’s changing. A growing revolution in imaging is making it possible for biologists to watch small-scale events as they unfold in living cells and tissues.
“The human brain is vision-focused,” says professor of molecular and cellular biology Jeff Lichtman. “If we see things, then we think we know what they mean.” To be able finally to see events that were known only in theory is incredibly satisfying for scientists. Even more important, this revolution also opens up the possibility of learning things about life that could never be studied before. Ironically, the technology enabling much of this change is the same one that launched the study of modern biology centuries ago: the light or optical microscope. A congruence of factors has shuttled these instruments back into the forefront of biology in recent years, after almost a half-century during which they were overshadowed by more powerful techniques such as electron microscopy and x-ray crystallography, which are able to create images on the level of single molecules.
More here. (Note: Do watch some of the stunning video images as well).