INCLUSION CRITERIA:  In order to be eligible to participate in this study, an individual must meet all of the following criteria:  Stated willingness to comply with all study procedures and availability for the duration of the study Male or female, aged >=18 years Current or previous diagnosis of any type of SCD (including HbSS, HbSC, HbSbeta0-thal, HbSbeta+-thal) Ability to travel to the NIH Clinical Center Ability of subject to understand and the willingness to sign a written informed consent document. Ability to undergo required studies except as specified in the Exclusion Criteria.  Curative Therapies Group  --Plan to receive conditioning for curative therapy at the NIH Clinical Center, Vanderbilt University Medical Center, or Johns Hopkins Hospital within a goal of within 90 days of conditioning, though transplants may need to be postponed for reasons beyond our control  Non-Curative Therapy Group  -- No plan to undergo curative therapy within 2 years  At least one of the following eligibility criteria:  History of stroke or abnormal transcranial doppler examination (>= 200 m/s) History of SCD-related renal insufficiency defined as a creatinine level >=1.3 mg/dL and kidney biopsy consistent with sickle cell nephropathy OR nephrotic syndrome OR creatinine clearance < 50mL/min Tricuspid regurgitant velocity >= 2.5 m/s Recurrent tricorporal priapism defined as at least 2 episodes of an erection lasting > 4 hours involving the corpora cavernosa and corpus spongiosa SCD-associated liver disease defined as EITHER ferritin > 1000 mcg/L OR direct bilirubin > 0.4 mg/dL > 1 hospitalization per year for vaso-occlusive crises while on a therapeutic dose of hydroxyurea Any acute chest syndrome while on a therapeutic dose of hydroxyurea Osteonecrosis of 2 or more joints Red cell alloimmunization  EXCLUSION CRITERIA:  All individuals meeting any of the exclusion criteria at baseline will be excluded from study participation.  Prior transplantation (including but not limited to HSCT and kidney transplant) Pregnant or breastfeeding Patients with allergy to iodine or iodinated contrast solutions will not undergo iothalamate GFR clearance testing but can undergo the other deep phenotype testing Acute painful crisis in preceding 4 weeks (patients with exacerbation of chronic pain can be enrolled per PI or designee discretion) Implanted metal object that is not compatible with MRI (e.g.: cerebral aneurysm clip, cochlear implant, or pacemaker) Patients with a pacemaker or automated implantable cardioverter defibrillator will not undergo VCTE but can enroll and undergo the other deep phenotype testing as long as the device is compatible with MRI and MRI testing can be performed Patients requiring peritoneal or hemodialysis Uncontrolled infection or acute illness  Criteria specific to the non-curative therapy group:  Hydroxyurea initiation or dose adjustment <2 months prior Initiation of chronic transfusion therapy <2 months prior Antihypertensive medication initiation or dose adjustment <1 month prior