Economic growth is the defining challenge of our time; without it, political and social instability rises, human progress stagnates and societies grow dimmer. But, says economist Dambisa Moyo, dogmatic capitalism isn't creating the growth we need. As she shows, in both state-sponsored and market-driven models, capitalism is failing to solve social ills, fostering corruption and creating income inequality. Moyo surveys the current economic landscape and suggests that we have to start thinking about capitalism as a spectrum so we can blend the best of different models together to foster growth.

Somersaulting manta rays, dashing dolphins, swarming schools of fish and munching sharks inhabit a world beneath the ocean's surface that few get a chance to see. Conservation photographer Thomas Peschak visits incredible seascapes around the world, and his photos reveal these hidden ecosystems. "You can't love something and become a champion for it if you don't know it exists," he says. Join Peschak in a new, immersive TED Talk format as he shares his stunning work and his dream for a future of respectful coexistence with the ocean.

Imagine having a surgery with no knives involved. At TEDMED, Yoav Medan shares a technique that uses MRI to find trouble spots and focused ultrasound to treat such issues as brain lesions, uterine fibroids and several kinds of cancerous growths.

An insect's ability to fly is one of the greatest feats of evolution. Michael Dickinson looks at how a fruit fly takes flight with such delicate wings, thanks to a clever flapping motion and flight muscles that are both powerful and nimble. But the secret ingredient: the incredible fly brain.

Alzheimer's doesn't have to be your brain's destiny, says neuroscientist and author of "Still Alice," Lisa Genova. She shares the latest science investigating the disease -- and some promising research on what each of us can do to build an Alzheimer's-resistant brain.

Using examples from vacations to colonoscopies, Nobel laureate and founder of behavioral economics Daniel Kahneman reveals how our "experiencing selves" and our "remembering selves" perceive happiness differently. This new insight has profound implications for economics, public policy -- and our own self-awareness.

As we expect more from technology, do we expect less from each other? Sherry Turkle studies how our devices and online personas are redefining human connection and communication -- and asks us to think deeply about the new kinds of connection we want to have.

The public is losing faith in democracy, says British MP Rory Stewart. Iraq and Afghanistan’s new democracies are deeply corrupt; meanwhile, 84 percent of people in Britain say politics is broken. In this important talk, Stewart sounds a call to action to rebuild democracy, starting with recognizing why democracy is important -- not as a tool, but as an ideal.

"For a long time, I lived for death," says Manwar Ali, a former radical jihadist who participated in violent, armed campaigns in the Middle East and Asia in the 1980s. In this moving talk, he reflects on his experience with radicalization and makes a powerful, direct appeal to anyone drawn to Islamist groups that claim violence and brutality are noble and virtuous: let go of anger and hatred, he says, and instead cultivate your heart to see goodness, beauty and truth in others.

Loretta Napoleoni details her rare opportunity to talk to the secretive Italian Red Brigades -- an experience that sparked a lifelong interest in terrorism. She gives a behind-the-scenes look at its complex economics, revealing a surprising connection between money laundering and the US Patriot Act.