An international expert group led by Bruijn at Leiden University in the Netherlands classified DN into four types, ranging from mild to severe disease from type I to type IV, based on the glomerular lesion characteristics of the renal biopsy tissue and with reference to the degree of interstitial and vascular lesions, in order for it to better guide the clinical management of DN. This panel is specified as follows: Type I, glomerular basement membrane thickening: under light microscopy, the biopsy tissue has only isolated glomerular basement membrane thickening and mild nonspecific hyperplasia. There was no glomerular thylakoid hyperplasia, no nodular hyperplasia of the thylakoid stroma or less than 50% sclerosis of spherical glomeruli. Type II, glomerular thylakoid hyperplasia: subdivided into mild (IIa) and severe (IIb). Kidney biopsy reveals mild to severe glomerular thylakoid hyperplasia without nodular sclerosis or less than 50% spherical glomerulosclerosis. Type III, nodular sclerosis: at least 1 glomerulus with enlarged thylakoid stromal nodules but less than 50% spherical glomerulosclerosis. Type IV, advanced diabetic nephropathy glomerulosclerosis: more than 50% spherical glomerulosclerosis and other clinical or pathologic evidence to support that the lesion is due to diabetic nephropathy.