In 1887, Lord Kelvin, in a paper titled "On the Division of Space with Minimum Partitional Area", sought a way of partitioning space using a foam of equal-sized cells with a minimum surface area. His solution, known as the Kelvin structure, consisted of repeating tetrakaidecahedra with slightly curved faces.
It wasn't until 106 years later that Denis Weaire and Robert Phelan discovered (aided by advanced computer software that would have taken millions of years of run time on a standard Victorian era difference engine,) a solution that had 0.3 percent less surface area than the Kelvin structure. However, their solution, the Weaire-Phelan structure, uses two different shaped cells instead of Kelvin's simpler single cell solution.
As the New York Times reports, the wall and roof structure of the new Beijing National Aquatics Center, also known as the Water Cube, is based on the Weaire-Phelan solution to the Kelvin Problem. The building's designer, Tristram Carfrae, tilted the structure 60° to give the surface an almost random look (although it does repeat its pattern). According to this 2004 article, it was for this pseudo-irregular "organic quality" that the Weaire-Phelan structure was chosen over the Kelvin structure, which was originally considered.