Carrie Partch was at the tail end of her postdoc when she made the first discovery. The structural biologist was looking at a database of human proteins, noting those that shared a piece with the ones she’d been studying. “I was just sort of flipping through it thinking, ‘I should know all of these,’” she recalls. “Then this one came up, and it had a different domain architecture than I’d ever seen.” She looked further into the protein, called PASD1, whose function was unknown. She found that among the few proteins it resembled was one called CLOCK. And that made her sit up straighter—because CLOCK is at the heart of a very large, mysterious process.