Around 1637, the French mathematician Pierre de Fermat wrote that he had found a way to prove a seemingly simple statement: while many square numbers can be broken down into the sum of two other squares - for example, 25 (five squared) equals nine (three squared) plus 16 (four squared) - the same can never be done for cubes or any higher powers. This book provides an account of how Fermat's solution was lost, the consequent struggle by mathematicians to solve this scientific mystery and how the solution was finally found in the 1990s.