The immune system surveys the body by sampling proteins, called antigens, from both the human host and any invaders. So how does the immune system keep from attacking the host?

Your fat is alive. Your fat is alive and it is talking. It is listening. It is reading its DNA and deciding what to make. It is coordinating more complex processes than an air traffic controller. It is smarter than Matt Damon in The Martian.

While our immune system functions to protect us from such things as invading microbes, these same defenses can also erroneously turn against the body.

This past weekend I sliced my finger while attempting to slice a carrot. The Wusthof cut through the nail on my left pinkie, aggravating a piece of flesh that, until that point, had successfully avoided combat.

As you read these words, hold out your hand. Notice the space between your fingers, the fragments of MacBook you can see through these windows. Think about how these digits formed, precisely arrayed and extended.

So much of science and medicine comes down to taking pictures. Biology, especially, has long been considered an observational enterprise.