Overview of Mammalian Thymic Development Biological Basis -- Embryology of the Mammalian Thymus -- Histogenesis of the Mammalian Thymus -- The Reticulo-Epithelial (Re) Cellular Network of the Mammalian Thymus -- Neuroendocrine Influence on Thymic Hematopoiesis Via the Reticulo-Epithelial (Re) Cellular Network -- Development of Lymphopoiesis as a Function of the Thymic Microenvironment -- The Hassal?s Bodies -- Thymic Accessory Cells, Including Dendritic Type Antigen Presenting Cells, within the Mammalian Thymic Microenvironment -- Involution of the Mammalian Thymus and Its Role in the Overall Aging Process -- The Thymus and Its Significance in Anti-Neoplastic Therapy -- Thymic Hormones in Cancer Diagnosis and Treatment -- Spontaneous Regression of Neoplasms: New Possibilities for Immunotherapy