Understanding how individual cells and complex brain networks interact in both time and space has been one of the grand challenges in the 21st century. In 2010, Lee et. al. have demonstrated that optogenetic fMRI (ofMRI) within the living mammalian brain reveals BOLD signals in downstream targets distant from the stimulation site, indicating that this approach can be used to map the global effects of controlling a local cell-type specific neuronal population. Since then, multiple studies have utilized ofMRI to dissect brain networks and properties. In this session, technical considerations in the application of ofMRI will be examined. Studies dissecting brain networks and properties using ofMRI will be reviewed. The opportunities and challenges will be discussed.