Relations are interesting

Relations are interesting. A single fact is not interesting. If it remains single, that is. We have to relate something to it to get it going.
A single table is moderately interesting. It invites us at first to build resumes and reports (discarding individual facts in the process; this is, by the way, deeply unsatisfying), and then to compare facts in proximity to each other.
Relations of multiple tables are very interesting.
Beyond that -- wait, what lies beyond that?
So many relations, branches and joins between tables that human beings cannot hold it all in their heads, I guess.