 So, what you're seeing here is a flow chart. It actually is called a Sankey diagram. It's a flow of energy across supply and demand for the United States. And up here on the left we're seeing coal, natural gas, crude oil that's produced from the United States as well as nuclear power and renewables. At the bottom you're seeing petroleum imports. Those are actually petroleum that we use in society that's coming from outside the United States. Our supply of energy is on the order of 108 quadrillion BTUs, otherwise known as quads. Quads is just a very convenient large number energy unit to use when we're talking about energy supplies and demands on a country-wide level. You're seeing that we have a supply of 20% of our energy from coal, 25 to 26% from natural gas. A large share for petroleum and what I want you to really focus on is that as of 2011, actually 2010 is apparently when this transfer became relevant, the amount of power from renewable energy that includes hydropower with wind and solar and others. That supply of energy became larger than our United States supply of energy from nuclear power. So we've got a really interesting significant change happening in the United States very recently and it's largely tied to the very large growth, very rapid growth of wind and followed by solar. The United States itself currently produces more energy than it actually demands. I've highlighted out in this slide two of the four sectors of energy demand. The residential and the commercial sectors are energy demand for the built environment for building systems. So residential buildings, your homes versus commercial buildings which could be thought of as schools, hospitals, retail stores. Industrial energy demand is tied to larger scale materials production, materials processing, fuel processing is industrial and then on the bottom we have transportation.