C# 5 has one big feature... asynchronous functions, aka "async/await". It's ever so exciting, whether you're writing client code which needs to have a responsive UI without turning your code into spaghetti, or server code where you really don't want to start 100,000 threads just because you've got a high traffic web server which needs to perform long-running tasks. In this talk I'll demonstrate what async functions look like, then dive into how they work under the hood. Be warned: once you've used C# 5, all other asynchronous code will look atrocious.