Innermost Essence (gsang ba snying thig). In general identical with the Instruction Section, the third of three division of Dzogchen. In particular it refers to the Innermost Unexcelled Cycle of Heart Essence (yang gsang bla na med pa'i snying thig gi skor), the fourth of the four divisions of the Instruction Section according to the arrangement of Shri Singha. All lineages of the Innermost Essence passed through Shri Singha and continued in Tibet through his personal disciples, Padmasambhava and Vimalamitra. In the 14th century these two lineages passed through Rangjung Dorje, the third Karmapa, and his close Dharma friend Longchen Rabjam (1308-1363), the latter of which systematized these teachings in his great body of writings. Longchen Rabjam was an incarnation of Princess Pema Sal, the daughter of King Trisong Deutsen, to whom Padmasambhava had entrusted his own lineage of Dzogchen known as Khandro Nyingtig. He is single-handedly regarded as the most important writer on Dzogchen teachings. His works include the Seven Great Treasuries, the Three Trilogies and his commentaries in the Nyingtig Yabshi. The practice of the Innermost Essence is continued to this very day.