Diabetic nephropathy (DN) also named diabetic kidney disease (DN) is one of the leading causes of mortality in people with diabetes. The aim of this review is to update the medical literature, the theories behind its early natural history, the pathways of its pathogenesis, its diagnosis and treatment. Poor glycemic control, hyperlipidemia, smoking, oxidative stress, accumulation of advanced glycated end products, environmental, genetic and epigenetic factors play an important role in the pathophysiological development of DN. Microalbuminuria has been traditionally used as the primary early diagnostic marker of microvascular complication unraveling the risk for progress to severe cardiorenal outcomes, but its prognostic role has been recently debated. The disease often leads to end-stage renal disease and it is often associated with major cardiovascular outcomes. Its early diagnosis is crucial for the patients in order to have a chance for proper treatment.