  The evolution of a quantum system under observation becomes retarded or even
impeded. We review this ``quantum Zeno effect'' in the light of the criticism
that has been raised upon a previous attempt to demonstrate it, of later
reexaminations of both the projection postulate and the significance of the
observations, and of the results of a recent experiment on an individual cold
atom. Here, the micro-state of the quantum system gets unveiled with the
observation, and the effect of measurement is no longer mixed up with dephasing
the object's wave function by the reactive effect of the detection. A procedure
is outlined that promises to provide, by observation, an upper limit for the
delay of even an exponential decay.
