Create new libraries
If the Aperture library becomes large, you can create additional, separate library files to hold…

View other libraries
When you have multiple Aperture and iPhoto library files accessible to your Aperture system, you…

Merge libraries
If you work with several computers, or work on projects with other people, you may…

Open your library in iPhoto
You can open your library in iPhoto from within Aperture. Choose File > Open Library…