Spermarche—also known as semenarche—refers to the beginning of development of sperm in boys' testicles at puberty. It contrasts with menarche in girls. Depending on their upbringing, cultural differences, and prior sexual knowledge, boys may have different reactions to spermarche, ranging from fear to excitement. Spermarche is one of the first events in the life of a male leading to sexual maturity. It occurs at the time when the secondary sexual characteristics are just beginning to develop. The age when spermarche occurs is not easy to determine. However, researchers have tried to determine the age in various populations by taking urine samples of boys and determining the presence of spermatozoa. This process of determining the sperm content in urine is referred to as spermaturia. From various sources, it appears that spermarche occurs between 11–15 years of age.