Kidney disease is a major cause of illness and death in people with sickle cell disease and sickle cell trait. Despite these concerning facts, we do not (1) have an in-depth understanding of how kidney disease starts in sickle cell disease and sickle cell trait, (2) have detailed insights into why kidney disease is worse in people with sickle cell disease and sickle cell trait, (3) have management options that are tailored to treating or preventing kidney disease in people with sickle cell disease or sickle cell trait. The SCeK Biorepository is a specialized, secure repository designed for the collection of blood and urine samples from people with sickle cell disease and sickle cell trait. These samples are connected to detailed medical records, with the sole purpose of allowing researchers to better understand how kidney disease starts and progresses in people with the sickle cell gene. By studying these stored samples (using new tests) together with health information, researchers can find better early warning signs of kidney injury and develop better ways to protect kidney health in people with sickle cell disease and sickle cell trait.