There is provided an aerosol generating device for heating an aerosol-forming substrate. The device comprises a storage portion (101) for storing the aerosol-forming substrate and a vaporizer (105; 105') for heating the aerosol-forming substrate to form an aerosol. The storage portion (101) has an outer housing and an internal passageway (103), the storage portion forming a reservoir for the aerosol-forming substrate between the outer housing and the internal passageway, and the vaporizer (105; 105') extends at least partially inside the internal passageway (103) in the storage portion(101). The device further comprises a porous interface (107) at least partially lining the internal passageway (103) for conveying the aerosol-forming substrate from the storage portion (101) towards the vaporizer (105; 105').