1. A method for managing items of inventory in a warehouse comprising: sending a request signal from a computer, the request signal specifying an item of inventory; receiving the request signal by a mobile drive unit (MDU), the MDU responding to the request signal by: determining a location of a movable inventory pod (MIP) that contains the item of inventory; energizing a drive mechanism of the MDU to move the MDU to the location of the MIP; docking the MDU to the MIP; energizing the drive mechanism of the MDU to transport the MIP to a station of the warehouse.