There is a new library Elements can live there Whats an Element? it's an instance of an Element Type What's an Element Type? It's a Document Type with 'Is Element Type' checkbox checked What's a Document Type? It defines an instance of Content Not a Content Type? No, a Content Type, means both a Document Type and a Media Type What's a Media Type? Is it a Document Type with 'Is Media Type' checkbox checked? No Media has its own section, the Media Library, IT IS different. Media Types are just Media Types, no checkboxes to check, that would be weird. Elements can live in the new section now though, the Library? errm, It's more about how they are stored in the database that is important is it? They are ultimately just Document Types What's a Composition? A Composition is not a thing...stop asking about compositions. A Document Type can define a composition and a Document Type can be composed of multiple compositions But not of a composition of a composition, because, you know, nested Document Types... What's a nested Document Types?, well a Document Type, instead of being curated from multiple compositions, can inherit properties from one parent Document Type, and that Document Type from a further grandparent Document Type and so on and so on, but of course, not if any of those Document Types use compositions. When I add a composition to a Media type, the text says I can inherit tabs and properties from an existing Document Type... but I can't, only a Media Type.