In recent years, the number of people suffering from diabetes has increased notably. This increase has led to an augmentation in secondary diseases; amongst them, diabetic nephropathy (DN) is one of the most relevant pathologies. DN provokes a decrease in glomerular filtration rate, which ends up in chronic renal failure. In the developed countries, DN is the first cause of chronic renal failure needing replacement therapy. Thus, this disease is responsible for a remarkable part of the public health costs in the Western countries. All of these facts have encouraged many scientists to perform their research on mechanism causing DN, improving our knowledge of its pathogenesis. In this review we summarize the most relevant facts on the physiopathology of DN.