David Hermlin is a singer, dancer, musician and songwriter — oh, and a global activist, too. Sample lyric: "I will fight for my dream, and I will never give up." Courtesy of David Hermlin hide caption

itoggle caption Courtesy of David Hermlin

They're members of the global-minded teens club: (left to right) Toluwanimi Sola-Adeyemi of Lagos, Chloe McGill of Seattle and Emine Arcasoy of Chapel Hill. Courtesy of Tolu Sola-Adeyemi, Chloe McGill and Emine Arcasoy. hide caption

itoggle caption Courtesy of Tolu Sola-Adeyemi, Chloe McGill and Emine Arcasoy.

Research into how the human brain develops helps explain why teens have trouble controlling impulses. Leigh Wells/Ikon Images/Corbis hide caption

itoggle caption Leigh Wells/Ikon Images/Corbis

An inmate at Rikers Island juvenile detention facility carries a plastic fork behind his back as he walks with other inmates. A recent report found that juvenile detainees are subjected to routine violence, both by other inmates and by correction officers. Julie Jacobson/AP hide caption

itoggle caption Julie Jacobson/AP

Jamira, 11, is an aboriginal girl in Australia. "I like being special," she says. "I like being — you know — different than everyone else." Henrik Nordstrom/I Am Eleven hide caption

itoggle caption Henrik Nordstrom/I Am Eleven

About 40 percent of high schools start before 8 a.m., which contributes to chronic sleep deprivation among teens, according to the American Academy of Pediatrics. Chris Waits/Flickr hide caption

itoggle caption Chris Waits/Flickr

Dr. Donald Brown inoculated Kelly Kent with the HPV vaccine in his Chicago office in the summer of 2006 — not long after the first version of the vaccine reached the market. Charles Rex Arbogast/AP hide caption

itoggle caption Charles Rex Arbogast/AP