About the Laboratory JINR's unique particle accelerators provide excellent possibilities for a wide range of radiobiological research. This fact has defined the fields of cellular and molecular biophysics research at JINR. In 1980s, JINR's biological research priority was given to the mechanisms responsible for difference in the relative biological effectiveness (RBE) of different types of ionizing radiation. RBE has long been one of the key problems in radiobiology. Although many radiobiological laboratories over the world devoted much effort to solving the RBE problem, the mechanisms responsible for different RBE of ionizing radiation with different linear energy transfer (LET) have not been revealed. The experiments carried out at JINR's heavy ion accelerators have shown that the biological effect of radiation with different LET is basically determined by the following two main factors: the microdosimetric characteristics of charged particles and the biological properties of the living cells; namely, their DNA repair capacity. It was inferred from experimental and theoretical studies that the DNA repair ability depends on LET since the nature of the lethal radiation-induced damage depends on LET. On the basis of the data on the specifics of the lethal action of different types of radiation on cells with different genotype, a wide research program aimed at thorough investigation of the mutagenic action of radiation with different LET on different bacterial cells was carried out. It was found that the linear quadratic dose – response dependence for mutation induction by gamma radiation does not change with increasing LET; the RBE coefficients of ionizing radiation grow with increasing LET; and the RBE(LET) dependence curve has a local maximum. The RBE(LET) dependence maximum for a mutagenic assay is shifted to lower LET in comparison with that for a lethal effect of irradiation. The frequency of mutations induced by radiation with different LET depends on the state of the cell reparation system. The determining role in mutagenesis belongs to the inducible SOS repair system; an increase in the genetic efficiency of radiation with an increase in LET is conditioned by a growing number of multiple DNA lesions repaired by the mutagenic branch of SOS reparation; the gene mutations in prokaryotes induced by heavy charged particles are caused by the delta-electron region of the particle track; and the difference in the position of the maximum of the RBE(LET) dependences for a mutagenic and lethal effects of irradiation is conditioned by the different nature of DNA lesions. The former (in the case of a mutagenic effect) are caused by multiple single strand breaks in DNA; the latter (in the case of a lethal effect), by double-strand breaks. The biological effectiveness of the radiation with different LET for the mutagenic assay is determined by the energy micro-distribution in genetic structures and the state of the genome and DNA repair system. The biological factor role in mutagenic efficiency of heavy charged particles also depends on LET. The main fields of research carried out now at the LRB are the following: Radiation Genetic Studies in Mammalian and Human Cells study of the mechanisms of stable and unstable chromosome aberration formation in human and mammalian cells exposed to heavy charged particles; study of mutagenic action of heavy ions on mammalian cells; study of low-dose irradiation effects on the chromosome system of mammalian cells; comet method study of the induction and reparation of DNA lesions by heavy ions. Radiation Research study of the radiation fields of JINR's basic research facilities and their environment; development of accelerator radiation shielding calculation methods; development of radiation shielding for accelerators built and upgraded at JINR and in its Member States; development of radiation detectors and dosimeters; radioecological research; physics support of the biological experiments at the JINR basic research facilities. Mathematical Modeling of Radiation-Induced Effects at the Molecular and Cellular Levels modeling DNA structure damage induced by radiations with different physical characteristics; modeling the mutagenic effect of ionizing radiations with different linear energy transfer in mammalian and human cells; modeling the molecular mechanisms of ionizing radiation-induced disorders of the central nervous system structure and functions. Radiobiological Studies of the Retina and Crystalline Lens study of the cataract genesis mechanism induced by heavy charged particles; study of radiobiological effects of heavy ion irradiation on the retina and visual pigment; study of the visual pigment structure by small-angle neutron scattering.