The Kagyu school of Tibetan Buddhism began in the 11th century with such renowned figures as Marpa and Milarepa, and it continues today with the Karmapa and several best-selling authors, including Pema Chodron and Chogyam Trungpa. Mahamudra, the "Great Seal, " is a central teaching of the Kagyu school, along with the so-called six dharmas of Naropa. Formulated as a systematic practice by Gampopa (1079-1153), the mahamudra teachings trace their source to earlier Indian materials and focus on the cultivation of profound insight into the nature of the mind.