What does an observed quantum system reveal to its observer?

The evolution of a quantum system under observation becomes retarded or eve n impeded. T;Ve review this "quantum Zeno effect" in the light of the criti cism that has been raised upon a previous attempt to demonstrate it, of lat er reexaminations of both the projection postulate and the significance of the observations, and of the results of a recent experiment on an individua l cold atom. Here, the microstate of the quantum system gets unveiled with the observation, and the effect of measurement is no longer mixed up with d ephasing the object's wave function by the reactive effect of the detection . A procedure is outlined that promises to provide, by observation, an uppe r limit for the delay of even an exponential decay.