The kidney is a structurally and functionally complex organ responsible for the control of water, ion, and other solute homeostasis. Moreover, the kidneys excrete metabolic waste products and produce hormones, such as renin and erythropoietin. The functional unit of the kidney is the nephron, which is composed by a serial arrangement of a filter unit called the renal corpuscle and several tubular segments that modulate the filtered fluid by reabsorption and secretion. Within each kidney, thousands of nephrons are closely intermingled and surrounded by an intricate network of blood vessels and various interstitial cell types, including fibroblasts and immune cells. This complex tissue architecture is essential for proper kidney function. In fact, kidney disease is often reflected or even caused by a derangement of the histologic structures. Frequently, kidney histology is studied using microscopic analysis of 2-dimensional tissue sections, which, however, misses important 3-dimensional spatial information. Reconstruction of serial sections tries to overcome this limitation, but is technically challenging, time-consuming, and often inherently linked to sectioning artifacts. In recent years, advances in tissue preparation (e.g., optical clearing) and new light- and electron-microscopic methods have provided novel avenues for 3-dimensional kidney imaging. Combined with novel machine-learning algorithms, these approaches offer unprecedented options for large-scale and automated analysis of kidney structure and function. This review provides a brief overview of these emerging imaging technologies and presents key examples of how these approaches are already used to study the normal and the diseased kidney.

肾脏是一个结构和功能复杂的器官，负责控制水、离子和其他溶质稳态。此外，肾脏排出代谢废物并产生激素，如肾素和促红细胞生成素。肾脏的功能单位是肾单位，它由称为肾小体的过滤单位和几个通过重吸收和分泌调节滤过液的管状部分的串联排列组成。在每个肾脏内，数以千计的肾单位紧密混合在一起，并被复杂的血管网络和各种间质细胞类型（包括成纤维细胞和免疫细胞）包围。这种复杂的组织结构对于正常的肾功能至关重要。事实上，肾脏疾病往往反映甚至是由组织结构的紊乱引起的。通常，肾脏组织学是使用二维组织切片的显微分析来研究的，然而，这会遗漏重要的三维空间信息。串行部分的重建试图克服这一限制，但在技术上具有挑战性、耗时，并且通常与切片工件有内在联系。近年来，组织制备（例如光学透明化）和新的光学和电子显微镜方法的进步为 3 维肾脏成像提供了新的途径。结合新颖的机器学习算法，这些方法为肾脏结构和功能的大规模和自动化分析提供了前所未有的选择。