Soldiers who've lost limbs in service face a daily struggle unimaginable to most of us. At TEDMED, Dean Kamen talks about the profound people and stories that motivated his work to give parts of their lives back with his design for a remarkable prosthetic arm.

Inventor Dean Kamen lays out his argument for the Segway and offers a peek into his next big ideas (portable energy and water purification for developing countries).

Inventor Dean Kamen previews the prosthetic arm he's developing at the request of the US Department of Defense. His quiet commitment to using technology to solve problems -- while honoring the human spirit -- has never been more clear.

Solar-powered LED lightbulbs could transform the lives of rural Haitians, but as Daniel Schnitzer found, they don't simply sell themselves. At TEDxPittsburgh, he shows how smart health and energy products for the developing world are useless unless the market works too.

Philosopher-comedian Emily Levine talks (hilariously) about science, math, society and the way everything connects. She's a brilliant trickster, poking holes in our fixed ideas and bringing hidden truths to light. Settle in and let her ping your brain.

Sherwin Nuland, a surgeon and a writer, meditates on the idea of hope -- the desire to become our better selves and make a better world. It's a thoughtful 12 minutes that will help you focus on the road ahead.

Clay Shirky looks at "cognitive surplus" -- the shared, online work we do with our spare brain cycles. While we're busy editing Wikipedia, posting to Ushahidi (and yes, making LOLcats), we're building a better, more cooperative world.

Iqbal Quadir tells how his experiences as a kid in poor Bangladesh, and later as a banker in New York, led him to start a mobile phone operator connecting 80 million rural Bangladeshi -- and to become a champion of bottom-up development.

Onstage at TED2012, Peter Diamandis makes a case for optimism -- that we'll invent, innovate and create ways to solve the challenges that loom over us. "I’m not saying we don’t have our set of problems; we surely do. But ultimately, we knock them down.”

In this unmissable look at the magic of comics, Scott McCloud bends the presentation format into a cartoon-like experience, where colorful diversions whiz through childhood fascinations and imagined futures that our eyes can hear and touch.

Physiatrist and engineer Todd Kuiken is building a prosthetic arm that connects with the human nervous system -- improving motion, control and even feeling. Onstage, patient Amanda Kitts helps demonstrate this next-gen robotic arm.

Daniel Kraft offers a fast-paced look at the next few years of innovations in medicine, powered by new tools, tests and apps that bring diagnostic information right to the patient's bedside.