Vibrational spectroscopy allows one to directly probe the structure and dynamics of biomolecules in aqueous solution. Two-dimensional infrared (2D-IR) spectroscopy has been shown to sensitively probe the secondary and tertiary structure of biomolecules and can be used to elucidate the ultrafast dynamics of protein folding. By spreading out the spectroscopic information over two dimensions, 2D-IR provides additional information on anharmonicities and on couplings between vibrational modes. Thus, it provides more detailed information than conventional, one-dimensional infrared spectroscopy.