Originally, he says, man was round, his back and sides forming a circle. Hermann Weyl, ``Symmetry'' (on Plato's Dialogue ``Symposium''). The evolution of polarization (alignment and orientation) of angular momenta of diatomic molecules both in the ground and excited states upon absorption of light is examined. The effect of external factors--magnetic field and collisions--on this polarization is investigated. Interference effects (level crossing, quantum beats, beat resonance) and the possibilities of employing them to determine magnetic and relaxation characteristics of individual vibration-rotation levels are analyzed. A classical description of phenomena is given in terms of distribution of angular momenta, including the use of isometric projections of the distribution being formed. Equations are given that describe the interaction of intense laser radiation with an ensemble of molecules in the gas phase. Other mechanisms are presented for the evolution of angular momenta for the ground electron state of diatomic molecules.