Erections occur when the penis fills with blood and stretches in shape and in size. Erections can last just a couple of minutes or much longer depending on the stimulation involved.

For most of the day, your penis is in a flaccid state (meaning it is soft). Erections can occur for any number of reasons, but are usually triggered by some sort of sexually arousing thoughts or stimulation. Young men typically begin getting erections during puberty as a normal part of their sexual development.