The right place at the right time.
D000818:Animals; D001853:Bone Marrow / Q000276:immunology; D006801:Humans; D007107:Immune System / Q000166:cytology*; D008198:Lymph Nodes / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology