Nephropathies arise from conditions that alter nephron development or trigger nephron damage during neonatal, juvenile, and adult stages of life. Much evidence suggests that a key role in maintaining kidney integrity, homeostasis, and regenerative capacity is played by a population of progenitor cells resident in the organ. Although the primary goals in the field of renal progenitor cells are understanding their ability to regenerate nephrons and to restore damaged kidney function, the discovery of these cells could also be used to elucidate the molecular and pathophysiological basis of kidney diseases. As a result, once the identification of a subset of progenitor cells capable of kidney regeneration has been obtained, the increasing knowledge about their characteristics and about the mechanisms of renal development had pointed out the possibility of understanding the molecular basis of kidney diseases, so that, nowadays, some renal disorders could also be related to renal progenitor dysfunction. In this review, we summarize the evidence on the existence of renal progenitors in fetal and adult kidneys and discuss their role in physiology as well as in the pathogenesis of renal disorders with a particular focus on childhood age.