We aim to explore new opportunities at ESRF beamline ID29 to investigate the reaction dynamics of proteins. For this we will investigate protein photoreceptors such as the Stigmatella aurantiaca bacteriophytochrome 2 (SaBphP2) on time-scales from 10 μs to 10 s. Phytochromes are light regulated enzymes where both light perception and enzymatic activity reside on the same polypeptide chain. The light signal is transduced from a central chromophore through about 150 Å to the enzymatic domain. The long term goal is to observe signal transduction and enzyme regulation in real time by using time-resolved, synchrotron based, serial X-ray crystallography (TR-SSX).