Study Design. This is a single-center case-controlled prospective observational study with the rationale of evaluating parameters of renal function including proteinuria, microalbuminuria and cystatin C in preterm infants and associating this with kidney size and blood pressure during the first 10 years of life. Demographics including race, gender and growth will provide important perspectives relative to formula and/or breast feeding with/without high calorie supplements during the first year.