Light micrograph of the epiphyseal growth plate of a developing long bone. At top, above the epiphyseal cartilage, is the epiphysis, with trabeculae of immature bone tissue separated by hematopoietic red bone marrow. In the cartilage, from epiphysis to diaphysis, the following layers are seen: zone of reserve, or resting; hyaline cartilage; zone of proliferation with typical seriated, or columnar, cartilage formed by chondrocytes in an arrangement resembling piles of coins; zone of hypertrophy with large lacunae; zone of calcification (not visible, but can be identified by the degeneration of the chondrocytes leaving empty cartilaginous lacunae); and an ossification zone of compact appearance, where there is an invasion of blood vessels and osteogenic cells.