Skin is marvellously complex, containing a hundred varieties of cells which seem especially sensitive to heat, cold, pressure and pain. By 32 weeks, nearly every part of the body is sensitive to the same light stroke of a single hair. The first dramatic motion, one that has come to symbolize life itself, is the first heartbeat at about three weeks after conception. Furthermore, use is necessary for development. Between week six and ten, fetal bodies burst into motion, achieving graceful, stretching, and rotational movements of the head, arms and legs.
Movement is spontaneous, endogenous, and typically cycles between activity and rest.
Breathing movements and jaw movements have begun. Hands are busy interacting with other parts of the body and with the umbilical cord. From this early stage onward, movement is a primary activity, sometimes begun spontaneously, sometimes provoked by events. Spontaneous movement occurs earliest, probably expressing purely individual interests and needs. Evoked movement reflects sensitivity to the environment.