Prisons can be considered "total institutions" that develop their own social structures and values. Inmates form prison subcultures to cope with deprivation. Two social structures exist - the official rules and the more powerful inmate social world. Over time, inmates may become "prisonized" and accept criminal values. Female prisons form "pseudofamilies" to replace lost relationships. Issues facing prisons today include aging inmates, inmates with mental illnesses, and preventing terrorism in corrections facilities.