The third phase of adolescence, late adolescence, is roughly from the ages of 17 to 21 years. During these years, your teen's physical development is basically complete, although boys may still grow a little taller, and your offspring may be able to have children of their own. By this age, the extreme self-consciousness of teens has faded and they're even willing to listen to what their parents have to say now and then. If parents and teens treat each other with respect, the potential for a close relationship is renewed. Instead of the peer group being all-important, late adolescents are now more interested in a few close friends and a serious relationship with a member of the opposite sex.
The more mature members of this age group no longer feel invincible, and risky behavior diminishes. Either through maturity or through accompanying their injured friends to the hospital and hearing them pronounced DOA (dead on arrival), they realize their mortality. They don't feel threatened by asking parents for advice and are able to express their ideas more clearly. The choice of college or work encourages late-adolescents to clarify their career goals, choosing which college they want to attend and what field of study they'll major in, or to join the labor force and grow from the responsibilities of a real job.
Once teens arrive at late adolescence, they may be able to see shades of gray where they formerly only saw black and white, and their capacity for problem solving and compromise has increased. In other words, they may be aware of subtle differences that change the whole picture and don't always see the world in terms of right/wrong and good/bad as they used to when they were in early or middle adolescence. Hopefully, you're proud of your teenager now that he or she has gone through the roughest years of adolescence, and you're ready to deal with the next sibling in line as he/she goes through a similar process.