In this talk I present a critical analysis of the notions of Events, States and Evolution in Quantum Mechanics. My analysis reveals a fundamental mechanism of dissipation in isolated open systems (systems of matter coupled to the quantized electromagnetic field). This mechanism is dubbed "Principle of Declining Potentialities" (PDP). When combined with a "State-Selection Postulate," PDP yields a precise law for the stochastic time-evolution of states of individual isolated open systems superseding Schrödinger evolution. This law yields a precise description of many phenomena, such as fluorescence, and a solution of the infamous "measurement problem."