A fascinating, ground breaking look at the new science around microbiomes, the ecological systems both within us and outside us that determine so much of our lives and the world around us.  Yong has done extensive and precise investigation of the field, spending time with dozens of cutting edge scientists, critically reading the scientific literature, and organizing the material into bite sized bits in this 357 page book.  While occasionally suffering from a tone of breathless excitement, Yong does an excellent job partly because he is the master of the perfect metaphor:  the ‘long waltz’ of symbiosis; the set designer role for genes that determine the microbiome; the metaphor of a wind that blows through two windows not affecting the home for the impact of probiotics eaten and expelled without any impact.  His basic argument is sound:  we are covered inside and out with billions of microorganisms which have traditionally been viewed as invaders and pathogens while in fact, they are critical to many of our mission-essential functions and contribute in ways still poorly understood to our survival and well-being.  Neologisms like dysbiosis, hologenome, synthetic biology, and concepts like the failed hygiene hypothesis, the FMT (fecal microbiota transplant), and the roles of microbes in building organs, calibrating immune systems, providing for unique skills (squid’s camouflage), evolutionary advantage, and chemosynthesis are all presented, discussed, and evaluated.  This is an important but not easy read.  I predict it will be a major award winner in year-end periodicals.