A storage system for storing product items, comprising a grid structure, where the grid structure has a top level; a number of first storage bins configured to be stored in vertical stacks in the grid structure, where each first storage bin is configured to contain at least one product item; a plurality of vehicles, arranged to move horizontally at the top level of the grid structure, and further arranged to pick up, carry, and place the first storage bins at desired locations within the grid structure; characterized in that - the storage system further comprises a robot device comprising a movable arm with a picking mechanism in one end thereof, - the robot device is configured to move a product item between a first location and a second location by means of its picking mechanism; - the first location is the location of a first storage bin stored in the storage grid, and in that the storage systemfurther comprises a storage control and communication system configured to:- control the vehicles to place a plurality of first storage bins in a first robot arm reachable area of the storage grid; and- control the robot device to move the product item from at least one first storage bin in the first robot arm reachable area of the storage grid at the first location to at least one second storage bin placed in a second robot arm reachable area outside of the storage grid at the second location. a grid structure, where the grid structure has a top level; a number of first storage bins configured to be stored in vertical stacks in the grid structure, where each first storage bin is configured to contain at least one product item; a plurality of vehicles, arranged to move horizontally at the top level of the grid structure, and further arranged to pick up, carry, and place the first storage bins at desired locations within the grid structure; characterized in that - the storage system further comprises a robot device comprising a movable arm with a picking mechanism in one end thereof, - the robot device is configured to move a product item between a first location and a second location by means of its picking mechanism; - the first location is the location of a first storage bin stored in the storage grid, and in that the storage systemfurther comprises a storage control and communication system configured to:- control the vehicles to place a plurality of first storage bins in a first robot arm reachable area of the storage grid; and- control the robot device to move the product item from at least one first storage bin in the first robot arm reachable area of the storage grid at the first location to at least one second storage bin placed in a second robot arm reachable area outside of the storage grid at the second location. - the storage system further comprises a robot device comprising a movable arm with a picking mechanism in one end thereof, - the robot device is configured to move a product item between a first location and a second location by means of its picking mechanism; - the first location is the location of a first storage bin stored in the storage grid, and in that the storage systemfurther comprises a storage control and communication system configured to:- control the vehicles to place a plurality of first storage bins in a first robot arm reachable area of the storage grid; and- control the robot device to move the product item from at least one first storage bin in the first robot arm reachable area of the storage grid at the first location to at least one second storage bin placed in a second robot arm reachable area outside of the storage grid at the second location.