This year there will be the 10th anniversary of the last edition of Encarta. One edition of Encarta was the first encyclopedia I ever read, and this was as a child. The big thing about Encarta was that it was not a paper encyclopedia. It was the first multimedia-based encyclopedia project. It was on CD-ROM and CD-ROMs can hold as much information as a much bigger, more expensive and heavier collection of books (which paper encyclopedias were), or hold more than that.
Additionally, articles contained relevant images, mostly in colour and some even had sound clips. But alas, Encarta didn't get as large as I once hoped it would. I do wish that an expert written encyclopedia could have made it to a million articles or more.