A method of generating an aerosol mist using a handheld device comprising a housing containing a sonic generator comprising a converter and an elongate horn having a proximal end coupled to the converter and a distal end that is arranged and configured to transmit sonic energy outside of the housing, and a power source coupled to the sonic generator; the method comprising the steps of: a) coupling a first unit dose capsule to the distal end of the elongate horn, the capsule comprising: i) a first portion comprising a deformable membrane adapted to releasably engage the distal end of the elongate horn and transmit sonic energy therethrough; ii) a second portion comprising at least one nozzle, wherein when coupled to the distal end of the elongate horn, the second portion is disposed in an outwardly facing orientation; and iii) a reservoir containing a liquid composition in communication with the at least one nozzle, wherein the deformable membrane forms a planar surface of the reservoir; b) energizing the sonic generator to deliver sonic energy to the first capsule coupled to the distal end of the elongate horn to generate an aerosol mist by forcing the liquid through the at least one nozzle by: i) engaging the distal end of the elongate horn with the deformable membrane of the reservoir, to drive liquid through the nozzle; ii) transmitting sonic energy through the deformable membrane to the liquid composition; c) removing the first unit dose capsule from the distal end of the elongate horn; d) coupling a second unit dose capsule to the distal end of the elongate horn; and e) energizing the sonic generator to deliver sonic energy to the second unit dose capsule coupled into the distal end of the elongate horn. a) coupling a first unit dose capsule to the distal end of the elongate horn, the capsule comprising: i) a first portion comprising a deformable membrane adapted to releasably engage the distal end of the elongate horn and transmit sonic energy therethrough; ii) a second portion comprising at least one nozzle, wherein when coupled to the distal end of the elongate horn, the second portion is disposed in an outwardly facing orientation; and iii) a reservoir containing a liquid composition in communication with the at least one nozzle, wherein the deformable membrane forms a planar surface of the reservoir; i) a first portion comprising a deformable membrane adapted to releasably engage the distal end of the elongate horn and transmit sonic energy therethrough; ii) a second portion comprising at least one nozzle, wherein when coupled to the distal end of the elongate horn, the second portion is disposed in an outwardly facing orientation; and iii) a reservoir containing a liquid composition in communication with the at least one nozzle, wherein the deformable membrane forms a planar surface of the reservoir; b) energizing the sonic generator to deliver sonic energy to the first capsule coupled to the distal end of the elongate horn to generate an aerosol mist by forcing the liquid through the at least one nozzle by: i) engaging the distal end of the elongate horn with the deformable membrane of the reservoir, to drive liquid through the nozzle; ii) transmitting sonic energy through the deformable membrane to the liquid composition; i) engaging the distal end of the elongate horn with the deformable membrane of the reservoir, to drive liquid through the nozzle; ii) transmitting sonic energy through the deformable membrane to the liquid composition; c) removing the first unit dose capsule from the distal end of the elongate horn; d) coupling a second unit dose capsule to the distal end of the elongate horn; and e) energizing the sonic generator to deliver sonic energy to the second unit dose capsule coupled into the distal end of the elongate horn.