The issue of aging has always been important for people during the development of mankind. In different epochs and cultures, this very issue was examined from different perspectives but the essence of it always stayed the same – people can not automatically become adults as soon as they are 21 or more. The main factor determining the status of an adult or a teenager, or a child, is the feeling of a particular person. This means that one who does not feel like a grown-up does not want to make a family, marry, or become a parent. In Asian cultures, the age at marriage is 13 – 14 years, while in the cultures of the Western Civilization this data is much more liberal. In the past young people used to marry and have children at the age of 20 – 21 and this seemed to be an adequate age for making such decisions and for beginning to feel adult (Devadason, 2007). But nowadays, the issue of adulthood is gradually becoming one of the most important because the borders between adolescence and adulthood are not fixed which leads to the mixture of generations, and to the process when large groups of people can not refer themselves to any of the existing age-groups. Scientists try to explain the phenomenon by giving various definitions and theories, but all these theories touch on one or several aspects of the topic. We consider that only the idea of Dr. Arnett covers properly all the sides of the adulthood issue and explains in detail the causes and effects of the aging phenomenon which transforming in today’s human society. This theory is called “The Theory of the Emerging Adulthood”, and the plot of this theory will be analyzed further in this essay. In order to avoid any possible ambiguity concerning the terms used in the work, we should at first define the specific phenomena. Firstly, adulthood is a period in a human’s lifespan when maturity in physical and mental regards is attained. It is commonly thought that adulthood is reached at the age of 20 or 21 but nowadays this common idea is being neglected by the events taking place in the modern world. That is why Dr. Arnett has developed his theory of Emerging Adulthood. Emerging adulthood, according to Dr. Arnett’s definition, is a period in a human’s life, between late teens and early or middle twenties (age of 18 – 21/25 years), when a person is no more a teenager, but not yet an adult. Adolescence is in the past but adulthood is not at present. There is no strict parents’ control, but there are also no adult responsibilities, so the person is free in his or her choices and actions but is somehow afraid of this sudden freedom (Arnett, 2001). The basis of the theory of Emerging Adulthood was taken by the author from the modern processes in the world. Dr. Arnett says that there is “a new and historically unprecedented period of the life course” (Arnett, 4) of young people, which can not be explained by any outside factors and demands only its internal consideration. According to the interviews and polls conducted by the author, there is a tendency in the modern world towards the increase of age at marriage and the age when people start feeling adults and planning families. From the given data we can clearly see that since the time of 1950s u