a fractal problem

[…] a fractal problem.

Fractal problems are those that look really simple from 100,000 feet up (like a dot) and reach unimaginable complexity as you get closer (like a fractal). There are a lot of problems of this nature (like email, transportation, ecommerce, taxation, etc.) and solving them is worth a lot of money but requires a LOT of work.

Source: https://news.ycombinator.com/item?id=6657087