(Spirit Rock Meditation Center) In the detailed description of the 16 steps of anapanasati (mindfulness of breathing) the first 12 steps develop samadhi (concentration) as a basis for the last four steps (13-16) of insight practice. These are using in and out breathing to become sensitive to impermanence (anicca), and from impermanence to releasing the agitation (viraga) from trying to find security in a fluid and fluctuating world. The second to last step in relaxing into the completeness and thoroughness of endings (nirodha), as a support to the last step of fully letting go.