Neutrons are proper tools for testing quantum mechanics because they a
re massive, they couple to electromagnetic fields due to their magneti
c moment and they are subject to all basic interactions and they are s
ensitive to topological effects, as well. Related experiments will be
discussed. Recent neutron interferometry experiments based on postsele
ction methods renewed the discussion about quantum nonlocality and the
quantum measuring process. It has been shown that interference phenom
ena can be revived even when the overall interference pattern has lost
its contrast. This indicates a persisting coupling in phase space eve
n in cases of spatially separated Schrodingercat-like situations. Thes
e states are extremely fragile and sensitive against any kind of fluct
uations and other decoherence processes. More complete quantum experim
ents also show that a complete retrieval of quantum states behind an i
nteraction volume becomes impossible in principle.