This book contains an up-to-date account of the experimental status of one of the fundamental and intriguing topic of contemporary physics, the one concerned with the concepts of Bohr's complementarity, non-locality and EPR non-separability of quantum objects. Different aspects, both conceptual and technical, of the complex fenomenology involving different quantum particles (neutrons, electrons, photons, atoms) are illustrated with a unifying perpective that enlightens the underlying basic processes. The book includes works by H Rauch (Vienna), S Haroche (Paris), D Greenberger (New York), A Tonomura (Tokyo), L Mandel (Rochester), H Walther (Munich), D Pritchard (MIT), R Chiao (Berkeley), J Franson (Baltimore), G Ghirardi (Trieste) and many others.