Prof. Dr. Thomas Oertner, head of the Institute for Synaptic Physiology at the UKE Hamburg, is convinced that synaptic long-term plasticity is the key mechanism of information storage in the brain. Tracking the strength of individual synapses over many days is challenging, but optogenetic manipulation and two-photon microscopy are non-invasive techniques that allow studying synapses in their natural environment. Latest results suggest that individual neurons keep track of past activity patterns and modify synaptic learning rules accordingly.