The first type of engineered wood to be invented. It is made from thin sheets of wood veneer, called plies or veneers. These are stacked together with the direction of each ply's grain differing from its neighbors' by 90°. The plies are bonded under heat and pressure with strong adhesives making plywood a type of composite material. A common reason for using plywood instead of plain wood is its resistance to cracking, shrinkage, twisting/warping, and its general high degree of strength.