  A quantum system being observed evolves more slowly. This `'quantum Zeno
effect'' is reviewed with respect to a previous attempt of demonstration, and
to subsequent criticism of the significance of the findings. A recent
experiment on an {\it individual} cold trapped ion has been capable of
revealing the micro-state of this quantum system, such that the effect of
measurement is indeed discriminated from dephasing of the quantum state by
either the meter or the environment.
