In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
Q: Before the honeycomb conjecture, these shapes were the subject of Thomas Hales' proof of the Kepler conjecture, which gives the most efficient way to pack these shapes into a space. A set consisting of the complex numbers and a point at infinity is called the Riemann type of this shape. It can be generated in cylindrical coordinates by setting r 2 + z 2 ["r squared plus z squared"] equal to a constant, and this shape can be generated in a coordinate system named for it by setting rho equal to a constant. Geodesics on this shape are called great circles, and the formula for its volume is four-thirds pi times radius cubed. Name this three-dimensional figure.
A:
Science