As the march of knowledge began and humans developed newer tools of exploring the universe, it was felt that science would triumph and it would not be long before the deepest mysteries of the cosmos would be laid bare. There was rapid advancement in all the branches of knowledge and everything appeared to be within the grasp of human intellect. However, that was not to be and our efforts were met with unexpected obstacles on the way. Although much has been discovered, yet much remains to be known. This book is a chronicle of the human endeavour in finding answers to some of the most exciting questions that have confronted us. Every chapter traces the attempts made by scientists and philosophers to provide answers to one such set of questions. Scientific discoveries have been presented in such a manner that a reader with little or no background in science can also grasp their essence. This book is useful not only for young minds curious to make sense of the world around them but also for any reader interested in understanding the deeper meaning of life and existence.