A continuous and potentially infinite composition of elements is enriched by a material duality in the Kreoo Tetris bookcase designed by Matteo Nunziati. The structure consists of horizontal wooden shelves, equally spaced, joined by wooden strips with a precious marble insert, which connect one or two shelves in height and draw a pattern that is never repetitive. The side profiles are fading and there is no defined perimeter in this essential game of parts which share the same thickness, both for horizontal and vertical surfaces.