This is a single-center sample study. A total number of 250 subjects will be consented and enrolled at Northwestern University Transplant clinic at the time of kidney biopsy. At our clinic, protocol biopsy may be performed at 3 months, 12 months , 24 months or any other time the doctor feels necessary post transplant in all kidney recipients. Kidney transplant recipients may also go under "for cause" biopsy procedure at any time point before/after or in between these protocol biopsy time points. Such causes of biopsy include increase in serum creatinine level, decrease in urine output, and/or pain at graft site.