This essay describes briefly population neuroscience, the merging of genetics and epidemiology with neuroscience, and its goals with regard to (1) gaining new knowledge about "processes" leading to a particular "state" of brain structure and function, and (2) using this knowledge to predict the risk (and resilience) of an individual for developing a brain disorder. It then argues that these goals are best reached by espousing a developmental perspective that acknowledges the importance of the time dimension (within and across generations) when studying multi-level factors shaping the human brain.