Several factors have incentive role for study of aging which includes increasing of the average and maximum of human life span, the increase in percentage of elderly in the societies and proportion of the national expenditure utilized by them. The Recent views of aging indicating that aging is extremely a complex multifactorial process despite of earlier views about definite cause aging like gene or decline of a key factor(1). This brief review tries to inspect aging at the molecular, cellular, and systemic levels; and consider interaction between genetic and environmental factors. Evolutionary theories argue that aging results from a decline in the force of natural selection. On the other hand, molecular theories emphasis on the genetically regulation of aging and argue that aging results from changing in genes. There are cellular theories that telomere theory is most famous. Stress induced aging is in this group too. free radical theory is next known way for cellular damages. Finally, we see systemic theories that contain two main groups, neuroendocrine and immunologic theories.