Turbulence is tricky to understand:

Big whirls have little whirls,
That feed on their velocity;
And little whirls have lesser whirls,
And so on to viscosity.

Lewis Fry Richardson (1881--1953), quotation from Goodreads: Lewis Fry Richardson: Quotes.

Actually, significant progress in understanding turbulence is being made circa 2017 (see, e.g., Davide Castelvecchi, Mysteries of turbulence unravelled, Nature, 2017aug21).