Liquid phase (also called “liquid cell”) transmission electron microscopy (TEM) is a powerful platform for nanoscale imaging and characterization of physical and chemical processes of materials in liquids. It is a direct approach to address critical scientific questions on how materials form or transform in response to external stimuli, such as changes in chemical potential, applied electric bias, and interactions with other materials or their environment. Answers to these questions are essential for understanding and controlling nanoscale materials properties and advancing their applications. With the recent technical advances in TEM, such as the development of sample stages, detectors, and image processing toolkits, liquid phase TEM is transforming our ability to characterize materials and revolutionizing our understanding of many fundamental processes in materials science and other fields. In this article, we briefly review the current status, challenges, and opportunities in liquid phase TEM. More details of the development and applications of liquid cell TEM are discussed in the articles in this issue of MRS Bulletin.

液相（也称为“液池”）透射电子显微镜（TEM）是用于纳米级成像和表征液体中材料的物理和化学过程的强大平台。它是解决材料如何响应外部刺激而形成或转化的重要科学问题的直接方法，例如化学势的变化，施加的电偏压以及与其他材料或其环境的相互作用。这些问题的答案对于理解和控制纳米级材料的性能以及促进其应用至关重要。随着TEM的最新技术进步，例如样品台，检测器和图像处理工具包的开发，液相TEM正在改变我们表征材料的能力，并彻底改变我们对材料科学和其他领域许多基本过程的理解。在本文中，我们简要回顾了液相TEM的现状，挑战和机遇。液体细胞TEM的开发和应用的更多细节在本期MRS公告。