Ultrafast 2D-IR spectroscopy is rapidly becoming a valuable tool for examining the relationship between structure and function of biomolecules. The unique combination of molecular-level structural information and ultrafast time resolution gives previously inaccessible insights relating to the rapid structural fluctuations, vibrational dynamics and solvent-solute interactions of proteins, all of which have important implications for the biological function of these species. In this tutorial review, the method and development of ultrafast 2D-IR spectroscopy is discussed, including an introduction to the two main experimental approaches, double resonance and photon echo 2D-IR, and the extension of the technique to non-equilibrium or transient 2D-IR measurements. The scope of the new information available through 2D-IR spectroscopy is then demonstrated by reference to the current state of the art of 2D-IR studies of molecules of biological interest.