There has never been a point in tine as the $20^{th}$ century where mankind has faced various Issues. During the past century, the human race has come to believe that the law of nature can be substituted by the development of science and technology. Scientists have worked on the atomic bomb and mainpulated the structure of the DNA. The $20^{th}$ century is a special landmark In human history. The various privileges that we are entitled to now are all the products of this century. The world population has Increased from 600 million In the 18u century to 900 million In the 19a century. This was larger due to the advance of science and technology during the 20u century. At this speed, it is anticipated that It will reach 30 billion by the end of the century. From a political perspective. there was turmoil. From an economic perspective, there were quantum leaps. The significant development of science and technology has enhanced the quality of human life. The $21^{st}$ century now awaits us. Things like memory cells and brain transplants may be realized and nuclear fusion may happen In the near future.