This book, Hydrogen Peroxide: A Health, Homeostatic and Protective Essentiality, verifies the crucial role of hydrogen peroxide, oxygen free radicals and electronically modified oxygen derivatives (EMODs) in healing, sexual function, reproduction, pathogen protection and cancer protection. Once again, we see that electronically modified oxygen derivatives (EMODs) are essential for homeostasis and normal functioning of the body and its organs. The fallen free radical theory has radically misled us many times for over half a century. Oxygen and its electronically modified oxygen derivative (EMOD) progeny are the sine qua non (the essential condition) of man's very existence. This is an inarguable fact. H2O2 is now recognized as a ubiquitous intracellular messenger under subtoxic conditions. Thus, get out of your head the concept that EMODs, and in particular hydrogen peroxide, are some cellular assassinating radical products generated only by angry PMNs. EMODs and hydrogen peroxide are intentionally generated salutary cellular products intended to help regulate critical metabolic and reproductive mechanisms. I believe that hydrogen peroxide is the most prevalent, and perhaps the most significant EMOD in the body, even exceeding the well recognized importance of nitric oxide. Hydrogen peroxide is ubiquitous, omnipresent and in steady state levels in all aerobic cells, due to its crucial protective role in sustaining and perpetuating mankind.