In a laboratory in Denver, on a decommissioned U.S. Army base, a baby sits in a high chair with two electrodes attached to his chest. To his left, on a small table, a muffin tin holds four numbered ...

I had a friend in San Francisco who would get all bent out of shape over baby carrots. “They’re not baby carrots,” she’d say. “They’re differently sized carrots.” I looked more closely. She was right.