the generation stage (utpattikrama) and the completion stage (nispannakrama). In the generation stage, one dissolves the mundane world and visualizes one's chosen deity (yidam), its mandala and companion deities, resulting in identification with this divine reality. In the completion stage, one dissolves the visualization of and identification with the yidam in the realization ultimate reality. Completion stage practices can also include subtle body energy practices, such as tummo (lit. "Fierce Woman", Skt. caṇḍālī, inner fire), as well as other practices that can be found in systems such as the Six Yogas of Naropa (like Dream Yoga, Bardo Yoga and Phowa) and the Six Vajra-yogas of Kalacakra. Dzogchen and Mahamudra Another form of high level Tibetan Buddhist practice are the meditations associated with the traditions of Mahāmudrā ("Great Seal") and Dzogchen ("Great Perfection"). These traditions focus on direct experience of the very nature of reality, which is variously termed dharmakaya, buddha nature, or the "basis' (gzhi). These techniques do not rely on deity yoga methods but on direct pointing-out instruction from a master and are often seen as the most advanced form of Buddhist practice. The views and practices associated with Dzogchen and Mahāmudrā are also often seen as the culmination of the Buddhist path. In some traditions, they are seen as a separate vehicle to liberation. In the Nyingma school (as well as in Bon), Dzogchen is considered to be a separate and independent vehicle (also called Atiyoga), as well as the highest of all vehicles. Similarly, in Kagyu, Mahāmudrā is sometimes seen as a separate vehicle, the "Sahajayana" (Tibetan: lhen chig kye pa), also known as the vehicle of self-liberation. Institutions and clergy Buddhist monasticism is an important part of the Tibetan Buddhist tradition, all the major and minor schools maintain large monastic institutions based on the Mulasarvastivada Vinaya (monastic rule) and many religious leaders come from the monastic community. That being said, there are also many religious leaders or teachers (called Lamas and Gurus) which are not celibate monastics. According to Geoffrey Samuel this is where "religious leadership in Tibetan Buddhism contrasts most strongly with much of the rest of the Buddhist world." According to Namkhai Norbu, in Tibet, Tibetan lamas had four main types of lifestyles: those who were monks, living in monasteries; those who lived a lay life, with their homes in villages; lay masters who lived as tent-dwelling nomads, travelling with their disciples, in some