The origins and contours of inmate social organization were once central research areas that stalled just as incarceration rates dramatically climbed. In this review, we return to seminal works in this area and connect these with six interrelated changes to correctional contexts that accompanied mass incarceration. We argue that changes in prison racial, age, crowding, gender, offense type, and managerial characteristics potentially altered inmate informal organization and have yet to receive adequate criminological attention. We review the few recent studies that document contemporary inmate social life and call for increased researcher-practitioner partnerships that achieve mutual goals and embed criminologists within carceral settings. We suggest that network approaches are particularly useful for building on past qualitative and ethnographic insights to provide replicable results that are also easily conveyed to correctional authorities. As the era of mass incarceration peaks, we assert that the time is ripe for renewed interest in inmate society and its connections to prison stability, rehabilitation, and community reintegration.