The article discusses on inflammatory renal disease, which may primarily affect each of the structural components of the kidney: glomeruli, tubules or interstitium. When glomeruli are inflamed (glomerulonephritis) there is a limited amount of space available for expansion, since the glomerulus is located within the confines of the Bowman's capsule. Accumulation of cells in Bowman's space, surrounding the glomerulus and compressing it, leads to an appearance in histological sections which is known as a 'crescent,' because this is often the shape taken up by the abnormal material.