The most successful female British pop musician in history, Annie Lennox has now committed herself to raising awareness of, and supporting actions against, the HIV/AIDS crisis in Africa.

Epidemiologist Seth Berkley is leading the charge to make sure vaccines are available to everyone, including those living in the developing world.

Emily Oster has a history of rethinking conventional wisdom.

How can mothers with HIV avoid passing it to their kids? In South Africa, Mitchell Besser tapped a new resource for healthcare: moms themselves. The program he started, mothers2mothers, trains new mothers to educate and support other moms.

Sunitha Krishnan is galvanizing India’s battle against sexual slavery by uniting government, corporations and NGOs to end human trafficking.

Danish political scientist Bjorn Lomborg heads the Copenhagen Consensus, which has prioritized the world's greatest problems -- global warming, world poverty, disease -- based on how effective our solutions might be. It's a thought-provoking, even provocative list.

Ernest Madu founded the Heart Institute of the Caribbean, a revolutionary clinic for cardiovascular diseases in Kingston, Jamaica -- revolutionary for offering first-class health care in a developing nation. His next stop: Nigeria.

In Elizabeth Pisani's latest book, she explores the "improbable nation" of Indonesia.

Through his William J. Clinton Foundation, former US President Bill Clinton has become a vital and innovative force for world change. He works in four critical areas: health, economic empowerment, citizen service, and reconciliation.

Kristen Ashburn's photographs bring us face-to-face with real people in desperate circumstances. Taking us to the intimate spaces of her subjects -- the victims of war, disaster, epidemic -- she elicits the sublime sadness and resolve of human beings in suffering.

Pastor Rick Warren is the author of The Purpose-Driven Life, which has sold more than 30 million copies worldwide. His has become an immensely influential voice seeking to apply the values of his faith to issues such as global poverty, HIV/AIDS and injustice.

Steven Addis is a father and photography buff who, by day, harnesses the power of branding for social change.

Armed with blood samples, high-tech tools and a small army of fieldworkers, Nathan Wolfe hopes to re-invent pandemic control -- and reveal hidden secrets of the planet's dominant lifeform: the virus.

TED Fellow Jane Chen has spent years working on health issues in the developing world.

Arik Hartmann is tackling the ignorance and misinformation surrounding HIV/AIDS.

Bono, the lead singer of U2, uses his celebrity to fight for social justice worldwide: to end hunger, poverty and disease, especially in Africa. His nonprofit ONE raises awareness via media, policy and calls to action.

Jessica Ladd is using technology to combat sexual assault, empower survivors and advance justice.

BCG's Johanna Benesty is a managing director and partner in the firm's Paris office.

Agnes Binagwaho helped rebuild the Rwandan health care system and continues to fight for positive change in global health.

At Gradian Health Systems, Erica Frenkel works to bring safe anesthesia to hospitals all over the world.

Debra Jarvis isn't your typical hospital chaplain. With wry wit, she aims to comfort patients -- and also challenge them.

Since 1974, Mechai Viravaidya has been creating and running innovative family planning and poverty reduction programs throughout Southeast Asia.

Lucy Marcil is providing fiscal services to low-income families in the doctor’s waiting room.

Carolyn Jones creates projects that point our attention towards issues of global concern.

Richard Sears thinks hard about the post-oil world. He's a visiting scientist at MIT, after a long career as a VP at Shell.

Our generation is the first in history with enough resources to eradicate hunger worldwide. Josette Sheeran, the former head of the UN World Food Programme, shares a plan.

Noreena Hertz looks at global culture -- financial and otherwise -- using an approach that combines traditional economic analysis with foreign policy trends, psychology, behavioural economics, anthropology, history and sociology.

In "The Cost of Hope," Pulitzer Prize winning journalist Amanda Bennett brings an investigative angle to the conversation about end-of-life care.

Julie Cordua is dedicated to building the tools, partnerships and communities that will eliminate child sexual abuse from the internet.

Amy Lockwood is the deputy director of Stanford's Center for Innovation in Global Health, where she looks at new solutions to big problems.