April 26, 1986 associates with the most severe catastrophic explosion and fire at reactor four of the nuclear power station at Chernobyl, Ukraine, in the former Soviet Union. The accident and the following fire released tremendous amounts of radioactive material into the environment that spread across Europe. More than 700,000 soldiers, miners, and workers were mobilized from all over the Soviet Union to liquidate Chernobyl’s aftermath, equipped just with shovels. About 135,000 people had been evacuated from the region and now it is a ghost town, with just few people of senile age, on average, 60 years old, who grow fruit and vegetables in the garden, keep agriculture, collect local berries and mushrooms, and go fishing, employees who are engaged in liquidation at the nuclear power plant and scientists who are studying a huge variety of wildlife. Ronald K. Chesser and Robert J.Baker are two scientists who went to Chernobyl in order to examine how radiation affects humans and animals and to evaluate molecular variations in organisms. They travelled to the “red forest”, named from predominant hue of the trees. Radiation killed all pine trees, only birches are remained. Scientists took the mice from the local area for the examination in a laboratory. Although, each mouse registered massive levels of radiation, all the animals seemed physically normal. Moreover, resident mouse population did not have any chromosomal damage. It seems that animals developed an immunity to harm from radiation. Indeed, after decline of the animal populations by radioactive fallout, wildlife now is thriving. Geologists noted that within five years after the accident, species returned and ecosystem reshaping took place. Today, The Chernobyl zone is a unique area, most of which is covered with dense vegetation and is inhabited by hundreds of species of animals, including those listed in the Red Book. In the dense thickets and marshes of the exclusion zone, endangered bird species such as the black stork, white-tailed eagle and eagle owl have found a house. Their populations are rapidly declining, there are only a few tens of thousands around the world, hundreds of these birds live in Ukraine. In the Chernobyl forests and rivers otters, badgers and lynxes have found shelter away from people. The absence of human intervention in their lives gives hope for the preservation of rare animal species and the growth of their populations.Speaking of genetic variation, scientists involved little rodents. They assumed that the genetic differences were caused by radioactive exposures, however, later on, they concluded that it was evolutionary time. Also, it is hard to take into account all factors that might have influenced genetic variation, for instance, geographical features, like forests, farmlands and rivers that differ across the regions may also affect gene expressions. Moreover, there is a broad range of different opinions about biological consequences of being exposed to radioactive environment near Chernobyl. Some studies concluded that mutation rates are exaggerated, other studies even failed to admit any increase in genetic mutations and difference in survival rates between animals from Chernobyl and those who are from clean areas. So, simply differences in opinions can lead to contradictory results of research.As well as scientists scrutinize how radiation affects animals, they also examine the level of risk to humans. In order to get objective knowledge about the effects of radiation on human beings, Life Span Study(LSS) is predicting what might happen to people who exposed to doses of radiation and analyzing the correlation between the diseases, like leukemia and cancer, and the amount of radiation. However, it turned out that the risks are low, because all people are constantly exposed to ionizing radiation from many natural sources, such as cosmic radiation and naturally occurring radioactive substances in all the foods we consume, the liquids that we drink, and the air we breathe. This is called natural background radiation. There is no evidence that this creates any risk to health.Turns out radioactive environment to Bess less hazardous that generally believed.