Mental illness is one of the most common health conditions—one in every eight people in the world lives with one. The staggering prevalence and impact of these illnesses has prompted worldwide research efforts to understand the causes and risk factors as well as to develop novel technologies and paradigms that more effectively diagnose and treat these illnesses. Today, therapeutic design efforts extend beyond those aimed at molecular and cellular mechanisms and include brain circuit organization and function. Such approaches offer the potential to link an individual’s symptom profile to personalized treatment for mental illness and open the door to new, innovative solutions for these conditions.