Abstract: An aerosol provision system (1) for generating an aerosol. The aerosol provision system comprises a first reservoir (31) for storing a first aerosol-generating material, wherein the aerosol provision system (1) is configured to generate a first aerosol using the first aerosol-generating material. The aerosol provision system 1 also comprises a second reservoir (101) for storing an active substance, or second aerosol-generating material such that the aerosol provision system (1) is configured to generate a second aerosol using the second aerosol-generating material. In this way, the first aerosol may be generated in a way which then allows the second aerosol, or active substance, to then be either added to, mixed with, and/or supplied alongside the first aerosol in a way which allows the user to effectively customise to what extent this first aerosol, which is delivered to the user, is supplemented with the second aerosol/active substance.