Revit Home Tab Tools Are Greyed Out!

This happens ALL the time with new students. At some point during my class, a student will comment about the Home tab and most of the tools on the Home tab as being unavailable or greyed out. This literally happens with every new class.

Revit does this on purpose. The reason this happens is because you are in the middle of another command which places you in edit mode or what we use to call sketch mode. I tell students to look at the upper right corner of their ribbon and if they see a colored tab, they need to select that tab and make it active. Once a student realizes this, they have to either finish edit mode by selecting the green check or cancel edit mode by selecting the red X.
Mark Petrucci