The author describes the different techniques of reconstructive surgery of peripheral nerves and the failures that marked these trials until the advent of microsurgical techniques. After stressing the importance of the biology and physiopathology of a traumatized nerve and its stem cells, the author detailes the regeneration stages of the nerve cell when ideal conditions of axonal alignment are established by microtechniques. Considering the different notions of biology and pathology in relation to the time delay between the traumatism and referral to the surgeon, the author insists on the absolute necessity of operating during the period of full regeneration of the nerve cell, i.e. within the first 6 months.