How to have both Gnome2 & Gnome3 ?

Hi, Is it possible to install Gnome3 as a separate desktop, ie. selectable from the login screen. So I have the option to choose Gnome2 or Gnome3 ? If so, How would I do it ?

Have you installed Gnome 3 ? Is it working properly ?

In my opinion it is not possible to make this. Only if you create a partition and install again the same operating system with GUI who you prefer.