A story map[9] is a graphical, two-dimensional product backlog. At the top of the map are big user stories, which are sometimes "epics" (big, coarse-grained user stories)[10] as Mike Cohn describes them, and other times correspond to "themes" (collections of related user stories[11]) or "activities". These grouping units are created by orienting at the user’s workflow or "the order you'd explain the behavior of the system". Vertically, below the epics, the actual story cards are allocated and ordered by priority. The first horizontal row is a "walking skeleton"[12] and below that represents increasing sophistication.[13][clarification needed]
In this way it becomes possible to describe even big systems without losing the big picture.