A storage system comprising: a first set of parallel rails or tracks extending in an X-direction, and a second set of parallel rails or tracks extending in a Y-direction transverse to the first set in a substantially horizontal plane to form a grid pattern comprising a plurality of grid spaces; a plurality of stacks of containers located beneath the rails, and arranged such that each stack is located within a footprint of a single grid space; at least one transporting device, the at least one transporting device being configured to selectively move laterally in the X and Y directions above the stacks on the rails, and configured to transport a container; a picking station configured to receive the container transported by the at least one transporting device; and a control unit for operation with a robot system comprising a sensor unit, the robot system configured to grasp an item (301, 302, 303) from a first container, and the control unit comprising: a verification unit configured to: receive identifying information of an item expected to be in the first container; receive information from the sensor unit indicative of a dynamics property induced by motion of the item grasped by the robot system relative to the sensor unit; and verify, before the item grasped by the robot system is placed in a second container, that the item grasped by the robot system matches the item expected to be in the first container based on the received identifying information and the received dynamics property information. a first set of parallel rails or tracks extending in an X-direction, and a second set of parallel rails or tracks extending in a Y-direction transverse to the first set in a substantially horizontal plane to form a grid pattern comprising a plurality of grid spaces; a plurality of stacks of containers located beneath the rails, and arranged such that each stack is located within a footprint of a single grid space; at least one transporting device, the at least one transporting device being configured to selectively move laterally in the X and Y directions above the stacks on the rails, and configured to transport a container; a picking station configured to receive the container transported by the at least one transporting device; and a control unit for operation with a robot system comprising a sensor unit, the robot system configured to grasp an item (301, 302, 303) from a first container, and the control unit comprising: a verification unit configured to: receive identifying information of an item expected to be in the first container; receive information from the sensor unit indicative of a dynamics property induced by motion of the item grasped by the robot system relative to the sensor unit; and verify, before the item grasped by the robot system is placed in a second container, that the item grasped by the robot system matches the item expected to be in the first container based on the received identifying information and the received dynamics property information. receive identifying information of an item expected to be in the first container; receive information from the sensor unit indicative of a dynamics property induced by motion of the item grasped by the robot system relative to the sensor unit; and verify, before the item grasped by the robot system is placed in a second container, that the item grasped by the robot system matches the item expected to be in the first container based on the received identifying information and the received dynamics property information.