Genealogy
A few years ago, I fell down the ancestry.com rabbit hole, and managed to make some basic diagrammatic sense of my family history back a few generations, until it became strangely addictive and frighteningly time-consuming. And cost too much money. So I suspended operations.
Then I stumbled across this chart, and it gave me such a popsicle headache that I had to stop looking at it. But I know some people for whom it will answer a lot of nagging questions, like “how do we refer to Great Aunt Bessie’s daughter?”
So have at it, all you amateur genealogists!