Every year, reporters and editors at Science choose several runners-up, and one Breakthrough of the Year.
Before we get to the Breakthrough, here are the runners-up.
In Mexico, researchers have drilled rock cores from the Chicxulub crater.
The cores chronicle in minute-by-minute detail the asteroid impact that wiped out the dinosaurs.
Other studies have revealed how the impact immediately destroyed living things thousands of kilometers away, and how mammals and plants recovered in the thousands of years that followed.
A team of physicists claimed its rudimentary quantum computer performed a calculation in 200 seconds, that would overwhelm a conventional supercomputer.
The achievement is known as quantum supremacy, and it marks a significant milestone on the long road to a fully functioning quantum computer.
Artificial intelligence systems have conquered a variety of complex two-person games.
But this year, a system called Pluribus upped the ante.
It beat professional players in thousands of six-hand games of no-limit Texas Hold 'em poker, a vastly more complex challenge.
