"Deity Yoga" (Tibetan: "lha'i rnal 'byor"; Sanskrit: "Devata-yoga") is a fundamental practice of Vajrayana Buddhism involving visualization of mental images consisting mainly of Buddhist deities such as Buddhas, Bodhisattvas and fierce deities, along mantra repetition. According to Geoffrey Samuel:If Buddhahood is a source of infinite potentiality accessible at any time, then the Tantric deities are in a sense partial aspects, refractions of that total potentiality. Visualizing one of these deities, or oneself identifying with one of them, is not, in Tibetan Tantric thought, a technique to worship an external entity. Rather, it is a way of accessing or tuning into something that is an intrinsic part of the structure of the universe — as of course is the practitioner him or herself.Deity yoga involves two stages, 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.