The Testicles (Testes) and Scrotum
The retractile testicles
Although the scrotum retracts against the body wall when it's cold, this also happens in conditions of fear and just before ejaculation.
Some men find that their testicles appear to spend most of their lives hugged close up to their body. If they never descend, medical attention should be sought.
Unequally sized testicles
This is normal. Nearly all men have testicles unequal in size. Sometimes this is very obvious from the way they lie in the scrotum, as in this picture.