Another episode of the on-going serie about interesting Endgame studies aimed at improving your tactical imagination (if you need to be convinced, just read here).
This 2 Knights against a Rook is an interesting fight...and quite painful for the weaker side!
Even though the bishop pair can be extremely powerful in open positions, the 2 knights duo are monsters in blocked or "messy" situations!
Also you certainly don't want to face them at the end of a Blitz game or in Zeitnot!
Below is a list of studies that will hone your skills and should demonstrate how powerful and difficult to face this duo can be.
A special mention of Alexey Troitsky (composer of two studies below) who is considered the father of the modern endgame study. If you are interested to know more about him, here is an interesting article about his work and legacy.