I can't explain it in medical terms. All I know is that By trapping as much bood into your penis as possible (with exercises like jelquing, squeezes, or whatever it is that your using), over time the tissues inside your penis will expand beyond what used to be. Girth is about expanding the chambers inside the penis from what I understand. Even though I dont completely understand the whole process from a deep physiologicall point of view, I have just use MY logic to put Penis Enlargement in perspective. Of course it works. You just have to FEEL that what your doing is working for you. The best reassurance wll be your own results!!! Good luck