Male anatomy of pleasure - the scrotum & testicles

And last but not least, a short article about those two things that are somewhat neglected, given the dominance of the penis...

The testicular sack (or scrotum) belongs to the primary erogenous zones of males. And it too shows a certain range of shape change: the skin of the scrotum is able to contract and relax. The testicles need a temperature slightly below core body temperature to produce sperm. That's why the testicles are located "outside" the body. The contracting and relaxing of the scrotum regulates their temperature.

The saggy or relaxed scrotum
The scrotum is most relaxed when it is warm, in order to bring the testicles further away from the body and keep them cool.

The half-contracted scrotum
The testicular sack usually contracts with sexual arousal. But not always, when it is too hot (in the literal sense), they remain saggy or somewhere in-between.

The contracted scrotum
The testicular sack always contracts when it is cold, so the testicles get warmer. Because they also do with sexual arousal, the contracted scrotum looks and feels very erotic (but tastes differ).

For more about this topic, see my post Keep them cool.