The microdosimetric approach permits to model the first physical stage of radiation damage developing of multistage model of radiation effect. It describes stochastics of absorbed energy distribution among and inside sensitive cell volumes. The analysis of radiobiological effect becoming more complete and adequate. The limits of application of valuable microdosimetric values to characterizing both the quality and quantity of radiation affecting the cells is considered. The aspects of the theory of dual action of radiation well compare with those of the cytogenetic model linking the reproductive cell death with asymmetrical chromosome exchanges.