Abstract: A MEMS actuator 1 comprising an actuator member 2 operably engaged by at least one actuator beam 4 and heating means 12 for heating the or each beam 4. The heating may cause expansion of the or each beam4, wherein the or each beam 4 has two ends A, A′ and the or each beam 4 is fixed at only one end A and wherein the expansion effects movement of the actuator member 2. The heating may cause thermal expansion of the beam 4 in one direction and longitudinal displacement of the beam 4 in the direction of thermal expansion, which longitudinal displacement effects movement of the actuator member 2. The beam 4 may act on the member 2 at a position in relation to a pivot point P so as to produce a torque which effects pivoting of the member 2 about the pivot point P. The actuator may have at least two actuator beams 4 and heating the at least two beams 4 may cause simultaneous expansion of the at least two beams 4, which simultaneous expansion effects movement of the actuator member 2.