A cartridge for use in an aerosol-generating system is described. One type of known aerosol-generating system is an electrically operated smoking system. In some types of electrically operated aerosol-generating devices, a reservoir of aerosol-forming liquid is provided in a tank. A problem of such a tank device is, that the system stops generating the aerosol if the device is held at such an angle that the liquid aerosol-generating substrate in the tank is not in contact with the capillary system. Moreover, these systems can be prone to leakage for example where the liquid from the tank floods the core or leaks through the airflow path. In other systems, the liquid storage portion of a cartridge is filled with a capillary medium. Although these systems reduce the above-mentioned problems of the holding angle and the risk of leakage, some residual liquid will remain in the capillary material after usage, leading to wastage. Further, there can be an inconsistency in puff deliveries in such systems due to decreasing saturation of the capillary medium during usage, which does not allow for a constant high-quality smoking experience. The cartridge described comprises a liquid storage portion comprising a housing for holding a liquid aerosol-forming substrate, wherein the liquid storage portion comprises at least two parts in fluid communication with each other. The first part of the liquid storage portion comprises a heater assembly, a first capillary material, provided in contact with the heater assembly, and a second capillary material in contact with the first capillary material and spaced apart from the heater assembly by the first capillary material. The second part of the liquid storage portion comprises a container for example a tank for holding aerosol-forming substrate in liquid form and supplying the liquid to the second capillary material.
