A customisable, modular storage system is described where goods are stored in containers and the containers are stored in stacks. The stacks are contained within towers formed of stacks of bin receiving units. A grid network of tracks is provided on the top of the bin receiving units upon which load handling devices run. The load handling 30 devices take containers from the stacks and deposit them at alternative locations in the stacks or deposit then at stations where goods may be picked out.