From Smithsonian Magazine, via an arXiv paper from 2023:
After decades of searching for what mathematicians call an “einstein tile”—an elusive shape that would never repeat—researchers say they have finally identified one. The 13-sided figure is the first that can fill an infinite surface with a pattern that is always original.
In the paper, the shape is called an aperiodic monotile which refers to its inability to repeat when tiled (aperiodic), and monotile meaning “one-tile”