In 1957, Huang and Yang predicted an asymptotic expansion for the ground state energy of a dilute Fermi gas in the thermodynamic limit that was accurate up to third order. Their formula revealed a remarkable universality: the correlation energy depends only on the scattering length of the interaction. In collaboration with C. Hainzl, P. T. Nam and R. Seiringer, we have provided a rigorous proof of this conjecture.