Abstract: A collapsible storage pen is disclosed. The pen having a segmented peripheral wall and interior wall segments forming a plurality of retaining cells, the interior wall segments being connected to the peripheral wall to move between an open position defining a rectangular periphery and a closed position wherein the wall segments are parallel and the length of the collapsed pen is less than the length of the longest side of the open pen. A method of forming the segmented peripheral wall and interior walls from a single blank of material is also disclosed.