This introductory chapter is divided into three sections. In the first section, we introduce the nonspecialist to the biology of the stress response through a brief history of the early studies on the stress or heat shock response. In the second section, we highlight aspects of the stress response, including the latest developments in the field, with emphasis on the function of the stress proteins. Finally, in the third section, an attempt is made to place the stress response in the perspective of human disease.