English: The penis and scrotum can contract involuntarily in reaction to cold temperatures or nervousness, referred to by the slang term "shrinkage", due to the body reducing blood flow to its appendages as well as action by the cremaster muscle. This is generally a normal and healthy function. During later shrinkage stages (4-6), the shaft skin covers the glans of this penis. This reinforces the fact that flaccid penile lengths vary greatly and are not a reliable measure. Notice that the scrotum is in a tense state due to the low temperature.