During 1923 to 1952, renal pathology coalesced around the integration of microscopic tissue patterns with emerging measures of kidney function. Researchers mapped distinctive glomerular lesions and honed classifications of nephritic disease, while recognizing systemic processes such as malignant hypertension as defining renal pathologies. The period also witnessed a turning point in diagnostic practice with the introduction of percutaneous renal biopsy, enabling in vivo histology and guiding treatment decisions. Concurrently, quantitative assessments of renal function using creatinine clearance and the evaluation of endogenous creatinine laid the groundwork for widely adopted metrics of glomerular filtration rate. Together, these approaches shifted the field toward a unified paradigm linking structure to function and prognosis.