Animation of the same plastic spheres disappearing one at a time.
A holy grail in pure mathematics is sphere packing in higher dimensions. Almost nothing has been rigorously proven about it, except in dimensions 1, 2 and 3.
That’s why it was such a breakthrough when, in 2016, a young Ukrainian mathematician named Maryna Viazovska solved the sphere-packing problem in eight dimensions, and later, with collaborators, in 24 dimensions.