A storage system comprising: a gridded three-dimensional structure comprising: a gridded lower track layout that occupies a two-dimensional area on which storage/retrieval vehicles are conveyable in two directions over said two-dimensional area; a plurality of storage columns residing above the gridded lower track layout in spaced distribution over the two-dimensional area of said gridded lower track layout, each column comprising a plurality of storage locations arranged one over another and sized to accommodate placement and storage of storage units therein; a plurality of upright shafts residing above the gridded lower track layout in spaced distribution over the two dimensional area of said gridded lower track layout, such that each of the storage columns is neighboured by respective upright shafts through which the storage locations of each of said storage columns are accessible by the storage/retrieval vehicles to place or remove the storage units to or from said storage locations of each of said storage columns; and at least one working station residing alongside the gridded three-dimensional structure and outside the two-dimensional area of the gridded lower track layout over which the storage columns and upright shafts are distributed; characterized in that said working station is joined to the gridded lower track layout by an extension track thereof by which said storage/retrieval vehicles are conveyable between said working station and said gridded lower track layout, whereby conveyance of the storage units between the storage locations and the working station is performed entirely by said storage/retrieval vehicles. a gridded three-dimensional structure comprising: a gridded lower track layout that occupies a two-dimensional area on which storage/retrieval vehicles are conveyable in two directions over said two-dimensional area; a plurality of storage columns residing above the gridded lower track layout in spaced distribution over the two-dimensional area of said gridded lower track layout, each column comprising a plurality of storage locations arranged one over another and sized to accommodate placement and storage of storage units therein; a plurality of upright shafts residing above the gridded lower track layout in spaced distribution over the two dimensional area of said gridded lower track layout, such that each of the storage columns is neighboured by respective upright shafts through which the storage locations of each of said storage columns are accessible by the storage/retrieval vehicles to place or remove the storage units to or from said storage locations of each of said storage columns; and at least one working station residing alongside the gridded three-dimensional structure and outside the two-dimensional area of the gridded lower track layout over which the storage columns and upright shafts are distributed; a gridded lower track layout that occupies a two-dimensional area on which storage/retrieval vehicles are conveyable in two directions over said two-dimensional area; a plurality of storage columns residing above the gridded lower track layout in spaced distribution over the two-dimensional area of said gridded lower track layout, each column comprising a plurality of storage locations arranged one over another and sized to accommodate placement and storage of storage units therein; a plurality of upright shafts residing above the gridded lower track layout in spaced distribution over the two dimensional area of said gridded lower track layout, such that each of the storage columns is neighboured by respective upright shafts through which the storage locations of each of said storage columns are accessible by the storage/retrieval vehicles to place or remove the storage units to or from said storage locations of each of said storage columns; and at least one working station residing alongside the gridded three-dimensional structure and outside the two-dimensional area of the gridded lower track layout over which the storage columns and upright shafts are distributed; characterized in that said working station is joined to the gridded lower track layout by an extension track thereof by which said storage/retrieval vehicles are conveyable between said working station and said gridded lower track layout, whereby conveyance of the storage units between the storage locations and the working station is performed entirely by said storage/retrieval vehicles.