A major outstanding challenge in neuroscience is to integrate across levels of investigation, linking genes, molecules, cells, microcircuits, regions, systems, and behavior. This will require bringing together evidence from sources across different spatial scales—from the microscopic, such as electrophysiological recordings in animals, to the macroscopic, such as conventional neuroimaging in humans. The mesoscale technique of depth-dependent fMRI, or “layer fMRI” which can be applied non-invasively in awake, behaving humans, is a critical missing link to bridge this gap.