A capillary aerosol generation system comprising: a source of pressurized liquid to be aerosolised; a capillary aerosol generator , and a valve between the source of pressurized liquid and the capillary aerosol generator , the capillary aerosol generator comprising: a capillary flow passage having an inlet and an outlet ; a heater in heat transfer communication with a first zone (Z1) of the flow passage; a heater in heat transfer communication with a second zone (Z2) of the flow passage, the second zone (Z2) being downstream of the first zone (Z1); and a controller in electrical communication with the heater for the first zone and with the heater for the second zone, the controller comprising a memory including an instruction set which instructs the controller when to measure the resistance of the heater in a zone, the current through the heater in a zone, the voltage across the heater in a zone, the power consumed by the heater in a zone and/or the temperature in a zone and when to apply voltage to the heater in the first zone (Z1), in the second zone (Z2) or in both, such that the liquid is volatilized and sprayed from a downstream end of the flow passage in the form of an aerosol. a source of pressurized liquid to be aerosolised; a capillary aerosol generator , and a valve between the source of pressurized liquid and the capillary aerosol generator , the capillary aerosol generator comprising: a capillary flow passage having an inlet and an outlet ; a heater in heat transfer communication with a first zone (Z1) of the flow passage; a heater in heat transfer communication with a second zone (Z2) of the flow passage, the second zone (Z2) being downstream of the first zone (Z1); and a controller in electrical communication with the heater for the first zone and with the heater for the second zone, the controller comprising a memory including an instruction set which instructs the controller when to measure the resistance of the heater in a zone, the current through the heater in a zone, the voltage across the heater in a zone, the power consumed by the heater in a zone and/or the temperature in a zone and when to apply voltage to the heater in the first zone (Z1), in the second zone (Z2) or in both, such that the liquid is volatilized and sprayed from a downstream end of the flow passage in the form of an aerosol. a capillary flow passage having an inlet and an outlet ; a heater in heat transfer communication with a first zone (Z1) of the flow passage; a heater in heat transfer communication with a second zone (Z2) of the flow passage, the second zone (Z2) being downstream of the first zone (Z1); and a controller in electrical communication with the heater for the first zone and with the heater for the second zone, the controller comprising a memory including an instruction set which instructs the controller when to measure the resistance of the heater in a zone, the current through the heater in a zone, the voltage across the heater in a zone, the power consumed by the heater in a zone and/or the temperature in a zone and when to apply voltage to the heater in the first zone (Z1), in the second zone (Z2) or in both, such that the liquid is volatilized and sprayed from a downstream end of the flow passage in the form of an aerosol. <EOS>