A MEMS flow sensor comprising: a body having a first semiconductor substrate and a second substrate bonded together, wherein the second substrate is one of: a semiconductor substrate and a glass substrate; a micro flow channel etched in the body and having an etched inlet opening at a first face of the body and an etched outlet opening at an opposite face of the body, the micro flow channel extending through the body from the etched inlet opening at the first face to the etched outlet opening at the opposite face; a film heater integral with the body and associated with the flow channel to heat fluid flowing through the flow channel; at least one film temperature sensor integral with the body and associated with the flow channel in a position spaced along the flow channel from the film heater, the at least one film temperature sensor operative to sense the temperature of fluid flowing through the flow channel, electronic circuitry integrated in the body and electrically connected to the film heater and the at least one film temperature sensor are operative to provide a signal representative of the rate of flow of a fluid flowing through the flow channel based at least in part on the temperature of fluid flowing through the flow channel sensed by the at least one film temperature sensor, and characterised in that the film heater and the at least one film temperature sensor form a first loop portion on the first semiconductor substrate and a second loop portion on the second substrate, and wherein the first loop portion and the second loop portion form a complete coil around the inside of the flow channel. a body having a first semiconductor substrate and a second substrate bonded together, wherein the second substrate is one of: a semiconductor substrate and a glass substrate; a micro flow channel etched in the body and having an etched inlet opening at a first face of the body and an etched outlet opening at an opposite face of the body, the micro flow channel extending through the body from the etched inlet opening at the first face to the etched outlet opening at the opposite face; a film heater integral with the body and associated with the flow channel to heat fluid flowing through the flow channel; at least one film temperature sensor integral with the body and associated with the flow channel in a position spaced along the flow channel from the film heater, the at least one film temperature sensor operative to sense the temperature of fluid flowing through the flow channel, electronic circuitry integrated in the body and electrically connected to the film heater and the at least one film temperature sensor are operative to provide a signal representative of the rate of flow of a fluid flowing through the flow channel based at least in part on the temperature of fluid flowing through the flow channel sensed by the at least one film temperature sensor, and characterised in that the film heater and the at least one film temperature sensor form a first loop portion on the first semiconductor substrate and a second loop portion on the second substrate, and wherein the first loop portion and the second loop portion form a complete coil around the inside of the flow channel.