Book excerpt: The book provides a comprehensive detailed summary of current status on skin microbiome research in health and disease as well as key regulatory and legal aspects. In the past decade, interest and technology have greatly advanced to unravel the nature and effect of skin microbiome on our health. Diseases such as atopic dermatitis and acne are at the forefront of this research, but also other conditions such as skin cancer are under investigation. In addition, mapping of the skin microbiome has gone from basic to more detailed with attempts to correlate it to various ages, ethnicities and genders. In parallel to mapping it, a great deal of research is dedicated to understanding its functionality and communication (and hence effect) on human cells. The Skin Microbiome Handbook is a summary of current status of knowledge, research tools and approaches in skin microbiome, in health and disease. It contains the following categories: healthy skin microbiome and oral-skin interaction; skin microbiome observational research; skin microbiome in disequilibrium and disease; skin's innate immunity; testing and study design; regulatory and legal aspects for skin microbiome related products. The 18 chapters of the book are written by carefully selected leaders in the academia and industry exhibiting extensive experience and understanding in the areas of interest.