The human brain growth and evolution have been subjects of many genetic, environmental or social studies separately. Additionally, there are very few available sources on the complex role of our microbiome and the recently discovered hormones VIP and PACAP. The book author also describes some of his cases seen during his long clinical experience to illustrate different points of his extensive literature review. The book is divided into seven chapters, condensing the author’s scientific opinion on the growth and evolution of the human brain, the organ that differentiates us from all other species. He does not dismiss any other opinions or beliefs. The author challenges scientists and clinicians to continue researching the brain without prejudice. At the end he gives his opinion on how our BIG brains can help us live better together.