Scrotal inflation (or infusion) is a procedure in which a saline solution is injected into the testicles to temporarily inflate them and give them that full, plump appearance. In some circumstances, men have injected up to 900 mL into their testicles, resulting in a scrotum resembling a large, red water balloon.
These pics were taken the day after I infused my nut sack with saline. You can see it has migrated into my cock. I hope to do an instructional video on this topic in the future. Do not try this without doing your research and or asking someone who knows what they are doing to help you.