Abstract: A media storage library using a horizontal cell array structure is provided. The library comprises an enclosure containing at least one horizontal array of storage cells and at least one picker robot that can move horizontally over the cell array by means of guide rails. Multiple horizontal cell arrays may be stacked vertically in separate rows, wherein the space between the rows is limited by the vertical height of the picker robot. The horizontal arrays may slide horizontally out of the library enclosure, creating an access pathway for human operators. In addition, multiple horizontal arrays may be arranged end to end within each row.