ssh x forwarding again

hallo, ssh x forwarding question: machine_inside ---- FW ----- internet ---- machine_outside can a user sitting on the secured by the firewall (FW) machine_inside ssh out to the machine_outside, then display an xterm from the machine_inside on the screen of the machine_outside? so that a user of the machine_outside can type commands on the machine_inside. this is important since i was told that this is possible. i do not see how it is doable; however, i am not an expert... if this is possible then ssh can be a door for people who do not have a dialup to get in from the outside but have ssh access... hope the above is understandable. thanks, -alexm