Neutrophil gelatinase-associated lipocalin (NGAL, also known as human neutrophil lipocalin, lipocalin-2, siderocalin, or LCN2) is a small molecule of almost 25 kDa that belongs to the well-defined superfamily of proteins called lipocalins. NGAL initially found in activated neutrophils, in accordance with its role as an innate antibacterial factor. However, it subsequently was shown that many other types of cells, including in the kidney tubule, may produce NGAL in response to various injuries. NGAL may become one of the most promising next-generation biomarkers in clinical nephrology and beyond.