This book stems from the belief that scientists and policy makers should be guided by the most reliable predictive models available, among which the hormetic dose response model has considerable evidence to support it, is very generalizable, has a strong mechanistic foundation and can be applied in the assessment of single agents and complex mixtures. For these reasons, the hormetic model should become the default in risk assessment.This book summarizes and analyzes the various positives of hormesis in an attempt to revel hormesis as a fundamental principle of toxicology, biology, and biomedical sciences as a whole. A focused discussion of how acceptance of the hormedis based model of toxicology would affect environmental standards and clean up values is mounted. A panel of scientists has been recruited to critically evaluate the hormetic dose response model and its comparison with current default models in their individual fields, including cellular biology, evolutionary biology, gerontology, and pharmacology. In-depth investigations are provided into how biological systems respond to increasing doses of environmental toxins while attempting to understand how cells respond to stress in the contexts of aging and neurological disorders.