Scrotum

The scrotum is basically a sack of skin that contains the testicles:


Note that I do not have an erection in this picture, I have simply lifted the penis to give a better view of what is behind it. Currently I feel comfortably warm, and thus the scrotum is relaxed and the testicles hang a bit from the body. Note that the left testicle is hanging lower: from what I have gathered, this is usually the case. Supposedly, this gives an advantage, since they then avoid clashing into each other when I move — or so I have heard. The two "strings" that seemingly goes from the testicles up to my penis is simply the result of how the loose skin of the scrotum folds when I stretch it like this.

When a man gets chilly, the scrotum contracts dramatically:


This way, the testicles are pressed closer to the body, in an effort to keep warm — but not too warm! The ideal temperature for sperm production is in a fairly narrow interval, some degrees below normal body temperature.

The scrotum is homologous to a woman's labia majora, i.e. they have the same origin. When the scrotum is contracted, we can more easily discern the so called perineal raphe, the "seam" that is the result of the two halves growing together during the fetal development.

Taking pictures of these parts of myself is actually harder than I thought! For a possibly clearer view of these features, see this picture of a man who has shaved his scrotum.