- Stem cell donor registries maintain databases of voluntary donors to facilitate life-saving bone marrow or peripheral blood stem cell transplants for patients with blood cancers, thalassemia, and immune disorders. - Human Leukocyte Antigen (HLA) matching is critical for successful stem cell transplantation, making genetic diversity within registries crucial, especially for underrepresented ethnic groups. - Registries utilize cheek swabs or blood samples to type a donor's HLA characteristics and list them anonymously until a match is found. - Collecting stem cells typically involves either peripheral blood stem cell (PBSC) collection (a non-surgical process similar to blood donation) or bone marrow harvesting. **Introduction** The article explains the concept, functioning, and significance of stem cell donor registries. It details how these registries match voluntary donors with patients suffering from fatal blood disorders and immune conditions using Human Leukocyte Antigen (HLA) typing. It also highlights the challenges of genetic diversity in finding matches and describes the two main methods of stem cell donation: peripheral blood stem cell (PBSC) collection and bone marrow donation. **Core Issue and Detailed Points** - Stem cell donor registries maintain databases of voluntary donors to facilitate life-saving bone marrow or peripheral blood stem cell transplants for patients with blood cancers, thalassemia, and immune disorders. - Human Leukocyte Antigen (HLA) matching is critical for successful stem cell transplantation, making genetic diversity within registries crucial, especially for underrepresented ethnic groups. - Registries utilize cheek swabs or blood samples to type a donor's HLA characteristics and list them anonymously until a match is found. - Collecting stem cells typically involves either peripheral blood stem cell (PBSC) collection (a non-surgical process similar to blood donation) or bone marrow harvesting.