Toilets and sanitation are one place where philanthropy and capital markets could come together to do something remarkable for the 2.5 billion people who don’t have safe access to a toilet—and whose communities carry a terrible health burden because of it. It’s an area that’s been almost completely ignored, but is now showing remarkable promise thanks to the inventive work of our research partners and others around the world. There’s a real market opportunity down the road, and the chance to improve the lives of the poor in the most tangible of ways. I spoke about it to my friend, Vinod Khosla, and some venture capitalists at the Khosla Summit in May.