A century ago, William James published The Varieties of Religious Experience. Today, a surprising proportion of the population of all belief systems report experiences referred to using terms such as ‘spiritual,’ ‘mystical,’ ‘peak’ or ‘transcendent.’ For example, about 30% of cross-cultural populations report having ‘felt at one with all things.’ Positive psychology includes the empirical study of positive mental states like these as one of its three pillars. This talk covers the causes (triggers), correlates (neurobiological changes), and consequences (outcomes) of these transcendent – and sometimes positively transformative – experiences.