August 19 marks the 11th annual World Humanitarian Day. The day honors people like UN humanitarian veteran Sergio Vieira de Mello, who lost his life in the UN Headquarters bombing in Baghdad in 2003. It is a tribute to aid workers worldwide, a commemoration to those who have lost their lives and a celebration of the spirit of humanitarian work around the world.

"Nurses, engineers and drivers, for example, all take great risk doing their work in sometimes extremely dangerous circumstances," said Valerie Amos, a UN Emergency Relief Coordinator, attending a memorial service in London for aid workers killed. "World Humanitarian Day is the day we remember the sacrifices that humanitarian workers make to support the most vulnerable."

As part of the World Humanitarian Day celebration, a new platform to inspire and mobilize action on global emergencies will be launched. The site – Messengers of Humanity – will build a community of thousands of advocates who will be asked to share content and stories on social networks. We hope that people will then be inspired to take action.

Karl Schembri of Save the Children has worked in Iraq, Lebanon, Jordan and Gaza this year: "Over the years, I have had the privilege to meet some of the kindest and most generous people. Their humanity in the face of all sorts of adversity should humble us all."

(WATCH the video with MTV DJ David Guetta, in honor of Humanitarian Heroes)