Light microscopy of a longitudinal section through a fetal finger. At this stage there is no bone tissue but rather a cartilage model acting as a precursor of the bone. All of the cells are chondrocytes. They are programmed to die but their secreted cartilage matrix (purple-red colour) provides the scaffold upon which bone matrix will later be deposited. The replacement of cartilage with bone is referred to as endochondral ossification.Magnification x90 when printed at 10 cm.