When it comes to mechanical puzzles it always comes to pieces. Often, the more the pieces, the harder the puzzle can be. In some puzzles the number of pieces can reach hundreds or even thousands. Jigsaw puzzles, for exampleWhen it comes to mechanical puzzles it always comes to pieces. Often, the more the pieces, the harder the puzzle can be. In some puzzles the number of pieces can reach hundreds or even thousands. Jigsaw puzzles, for example. More intriguing is to take a look at the opposite end of the spectrum. A set consists of at least two pieces. Hence the question: are there any 2-piece puzzles which can really baffle? Fortunately, the answer is “Yes!” Several preconditions had been considered while selecting the puzzles for this review. 1. A puzzle must not be trivial. 2. The pieces can be compound ones provided that if such a piece is broken into at least two smaller pieces the idea of the puzzle is totally broken. 3. Very specific cases of the 2-piece puzzles such as mazes (board as one piece and the moving object as another) weren't considered for this review. Good luck and Happy Puzzling!