1. A modular warehouse system comprising: at least two modular stackable bins wherein said bins allow retrieval of at least one of said bins, regardless of its location in the pile, without changing said pile's order, each of said bins includes top side, bottom side, right side and left side, each of the top side, bottom side, right side and left side is provided with a wheel and a slot, the slot receives the wheel of a corresponding one of the top side, bottom side, right side and left side of another one of said bins, thereby providing engagement to support said bins by each other; at least two bin retrieval robots; at least one non-transitory computer-readable medium storing processor executable instructions on a computing device for warehouse management, adapted to: manage said warehouse inventory; manage said at least two bin retrieval robots; and allow user to simulate scenarios related to said warehouse system and present said simulations results to said user via a user interface; wherein said modular warehouse does not require shelving.