While there are many good books in particle physics, very seldom, if ever, has a non-specialist comprehensive description of quantum field theory appeared. The intention of this short book is to offer a guided tour of that innermost topic of theoretical physics. Written in plain English and avoiding the mathematical apparatus, but still describing its various facets up to the research frontier, this book gives a glimpse of what the human mind has been capable of imagining for dealing with the behaviour of nature at the most fundamental level.