...to study the basic biophysical mechanisms enabling animals to sense the required cues in their environment. In this project we will use different ultra-fast electronic spectroscopy techniques to elucidate the fundamental charge and spin transfer processes underlying radical pair formation in cryptochromes. These experiments shall selectively probe the dynamics of radical pairs in their singlet and triplet states, provide evidence for coherent singlet-triplet interconversion and, thus, test a cornerstone of the currently proposed models for radical-pair based magnetoreception.