Exercise. Arm exercises such as biceps curls are excellent for increasing bicep size. Search around google for a video or ask a personal trainer at your local gym for other great exercises.
No, How do they become bigger, not, how can i make them bigger
Ah, well then you're asking about the mechanisms of muscular hypertrophy. Look no further:
By doing bicep workouts like the dumbbell curl, barbell curl, using bicep machines, bench press, and taking proper supplements like protein shakes and nitric oxide.
Ultimately, the size of your penis is determined by genetics. But you can increase its apparent size by shaving the pubic hair at its base. You can also get a slight increase in size by holding off...