 Grand challenges describe the greatest, most persistent, and most pervasive problems facing humanity. At XPRIZE, we think of grand challenges as the factors that are preventing progress, the barriers that stop us from moving forward. They prevent us from achieving a desired future. Grand challenges are usually a product of various global conditions. These can be social, political, cultural, economic, or a complex combination of many. But they can also help us pinpoint the world's most promising opportunities. A grand challenge needs some sort of breakthrough to surpass the stubborn problems it entails. But what are breakthroughs? For XPRIZE, a breakthrough is a discovery or disruption that dramatically changes the trajectory of the future. They help us in achieving our desired future, one in which humanity has managed to overcome the grand challenges in a particular area or domain. XPRIZE competitions encourage technological innovations that will spark radical progress toward these breakthroughs. Possible breakthroughs are carefully selected for their ability to truly change the world. New financial and economic models, changes of regulations, global cooperation and agreements, and of course, technological innovation, breakthroughs come in many shapes and forms. The possibilities are endless. So when XPRIZE talks about breakthroughs in a particular topic area, we've made sure the ideas have a real chance of making a difference. And we suggest a wide array of potential breakthroughs. What's your breakthrough?