A measuring head for a nano-indentation instrument capable of positioning a sample relatively to the measuring head, which includes a measuring axis, a reference axis and a component for detecting a depth of penetration of an indentor into the sample. The measuring and reference axes are attached to a frame for connection to the instrument. The measuring axis incorporates an actuator and includes the indentor, the reference axis incorporates an actuator and includes a reference tip, and the measuring and reference axes each have a component for detecting a force applied by its actuator. Penetration depth is detected by measuring a displacement of the indentor relatively to the reference tip.