This article gives an introduction to a long-term project called Flyspeck, whose purpose is to give a formal verification of the Kepler Conjecture. The Kepler Conjecture asserts that the density of a

packing of equal radius balls in three dimensions cannot exceed $pi/sqrt{18}$.

The original proof of the Kepler Conjecture, from 1998, relies extensively on computer calculations. Because the proof relies on relatively few external results, it is a natural choice for a formalization effort.