The fibroblast, major cell of connective tissue, secretes the various elements of interstitium: collagens, proelastin, glycoproteins and proteoglycans. It maintains the turnover of these structures and intervenes, also, in the cholesterol LDL metabolism. These various properties explains its different morphological aspects. In young patients, it is an active secretory cell. Its voluminous cytoplasm contains a well developed endoplasmic reticulum and others organelles. It is always in close connection with collagen fibers. The cytoskeleton consists of a fine network visible throughout the cytoplasm and near of secretory areas. In adult patients, the fibroblast keeps the same characteristics, but the endoplasmic reticulum is poorer than in young subjects. In old patients (physiologic or pathologic ageing) it becomes a quiescent cell. It is a flattened cell; its cytoplasm contains a poorly developed endoplasmic reticulum and numerous dense bodies. Its cytoskeleton is characterized by voluminous fascicles or bundles of microfilaments into large cytoplasmic areas. This modified fibroblast has not direct contact with collagen. In all cases, various stimuli can: activate the fibroblast. Then this cell becomes a large cell with very abundant reticulum endoplasmic, ribosomes, polysomes, and numerous secretory vesicles. It is an active secreting cell; becomes fibroblast and; change into myofibroblast by presence of myofilaments in its cytoplasm.