Grasshopper is a new plug-in that David Rutten is working on for Rhino. It has similar functionality to GC but at this point if not so component based. It is more like GC in that it uses features and stores them as nodes you can rearrange and change hierarchy's. In this video David covers where to find the plug-in, how to install it and then the very (let me emphasize the VERY) basics of the interface. Learn how to install and get started using the Explicit History plug-in (also known as Grasshopper) in Rhino. The tutorial is best viewed at full screen.