Anapanasati, mindfulness of breathing, is set out canonically in the Anapanasati Sutta of the Pali Canon, where the Buddha teaches the practice as a structured sequence of sixteen steps grouped into four tetrads, each tetrad building on the last: the first attends simply to the breath as it comes and goes, long or short, the second extends that attention to the whole body and its calming, the third moves to observing mental and emotional states as they arise alongside the breath, and the fourth turns toward insight into impermanence, dispassion, cessation and letting go, so that the practice is presented in the earliest sources not as a single technique but as a complete graduated path moving from simple physical attention through to the tradition's deepest liberative aims. The sutta explicitly links anapanasati to the four foundations of mindfulness, satipatthana, treating breath awareness as the specific method through which body, feeling, mind and mental phenomena, the sutta's fourfold framework for the whole of Buddhist mindfulness practice, can each in turn be brought into clear observation, which is part of why the practice holds such a central and frequently cited place across the whole of the Theravada meditative tradition and, in adapted forms, well beyond it.