In this ossification, 1) chondrocytes and lacuna get bigger, calcify, and then the cell dies leaving holes. 2) Blood vessels grow into perichondrium, first become osteoblasts and then they create a layer (perichondrium is now periosteum). 3) Blood vessels enter space from dead chondrocytes. Fibroblasts in blood supply form more osteoblasts and make spongy bone. The formation spreads. 4) Bone grows, osteoclasts begin remodel. 5) Capillaries and osteoblasts move into epiphyses, creating secondary ossification centers. 6) Epiphyses fill with spongy and articular cartilage and epiphyseal cartilage remains.