Three Internal Tantric Vehicles

Also referred to as "internal tantras," these final three systems and corresponding texts are on the whole unique to the Nyingma tradition. Some Nyingma scholars as early as the fourteenth century correlated these final three systems with the three internal divisions of the "modern" (gsar ma pa) Unsurpassed Yoga tantras: Mahāyoga tantras with the "father" tantras (emphasizing "generation phase" of tantric contemplation), Anuyoga tantras with the "mother tantras" (emphasizing "perfection/completion phase" of tantric contemplation), and Atiyoga tantras with the "Non-dual tantras" (the two phases are non-dual).