The Priority Program 1665 aims at identifying causal relationships linking the activity of single neurons and networks to behavior. Emphasis will be laid on sensory-motor and cognitive processing. Investigations will be performed at different levels of network complexity, ranging from single neurons and microcircuits to large-scale cortico-subcortical neuronal networks and both adult and developmental aspects will be covered. Specifically, 38 research groups from universities and research centers all over Germany have built 12 “troika collaborations”. They include “experimenters”, i.e. groups resolving or manipulating neuronal activity, “toolmakers”, i.e. groups developing and validating the recording and manipulation methods, and “analysts”, i.e. groups analyzing network dynamics or dissecting the functional readout.