The icOS Lab is essentially dedicated to the recording of optical spectroscopy data from crystals of proteins, nucleic acids and smaller molecules, or on nanolitres of concentrated solution. Available spectroscopies include UV-Visible light absorption, fluorescence emission and Raman. Measurements can be performed on steady states at cryogenic or room temperature, or using a time-resolved approach (pump-probe or continuous) at room temperature. The lab is run in the context of a close collaboration between the MXIS Group of the ESRF and the Synchrotron Group of the IBS, as one platform of the Partnership for Structural Biology.