Probably most people don't realize that Fisher isn't even the youngest member of the men's team. Myles Marshall of Kingwood, TX made it in the 800m (time of 1:48.43) and is 7.5 months younger than Fisher. Sophomore Josephus Lyles (15 months younger than Fisher) finished 4th in the 400m to make it in the 4x400m relay.
Full team list here:
http://www.usatf.org/News/USATF-announces-Team-USA-roster-for-IAAF-World-Jun.aspx