Scarring is the name given to fibrous tissue accumulation in the skin, which, when it forms elsewhere, is known as fibrosis, but the terms are frequently used interchangeably. The scientific study of fibrosis or scarring was established and developed in skin wounding, as a part of the normal repair response, long before it was appreciated that pathological fibrosis or scarring occurs as a consequence of sustained or iterative injury to internal organs. Increasing experimental evidence indicates that the process of skin wounding with scarring is very similar to the process of organ injury with fibrosis detected in vital organs including the kidney. Kidney fibrosis develops in glomeruli, where it is known as glomerulosclerosis (literally hardening of glomeruli due to fibrotic tissue), or in the interstitial virtual space between tubules and peritubular capillaries, known as interstitial fibrosis. Increasingly fibrosis of the kidney and the cells that make fibrous tissue are seen as targets for therapeutic intervention in chronic diseases of the kidney.