... and yield statement
http://www.cpudreams.com/2010/02/coroutines.html
http://jxs.me/2010/05/14/using-yield-in-c/
http://unity3d.com/support/documentation/ScriptReference/index.Coroutines_26_Yield.html
http://www.youtube.com/watch?v=Ia616pWH2QA