Apparatus for vaporizing liquid in a vaporization pathway having an actively controlled temperature are disclosed according to some aspects. The apparatus can comprise a first body having a cross sectional shape and dimensions substantially equal to the cross sectional shape and dimensions of a cavity in a second body, which allows the first body to be non-permanently inserted into the second body. The outer surface of the first body, the inner surface forming the cavity in the second body, or both can be modified to create a vaporization pathway between the first and second bodies when the surfaces mate and/or align. The liquid vaporizer can further comprise a vaporization pathway inlet for fluid comprising liquid, a vaporization pathway outlet for fluid comprising primarily vapor, and a heater in thermal communication with the first body, the second body, or both. The heater provides active control of the temperature of the vaporization pathway.