In terms of Biology humans are just another species on this planet, but when it comes to explaining the biology of the context of Human behavior, it really becomes very tough. Humans have the physiology and anatomy similar to that of a cave man, yet the level of our intelligence has far evolved in comparison to the extent that the cave man anatomy and physiology becomes inadequate to serve to the needs of certain aspects of human intelligence of modern times which essentially functions beyond the level of just survival (for example in animals), and is capable of performing such advanced functions as retaining a huge past memory and can anticipate a future situation. This in many ways has made us far superior to the animal world, yet many of us get messed up in handling our intelligence properly and either develop chronic stress, indulge in violence or mishandle the adolescence related issues of our teenagers. Biologically speaking human behavior is determined largely by how our brains are shaped by developmental and evolutionary processes, at the heart of which lies the genetic and epigenetic changes and environmental impact. Because at any critical moment brains are to decide about any bit of a behavior, therefore the knowledge of underlying brain anatomy and physiology is important. This article is about explaining how biology makes a sense to human behavior and is essentially focused on its three important aspects, i.e. adolescence, chronic stress and violence, which are described in detail in the following paragraphs.