Neutral-atomic and molecular outflows are a common occurrence in galaxies, near and far. They operate over the full extent of their galaxy hosts, from the innermost regions of galactic nuclei to the outermost reaches of galaxy halos. They carry a substantial amount of material that would otherwise have been used to form new stars. These cool outflows may have a profound impact on the evolution of their host galaxies and environments. This article provides an overview of the basic physics of cool outflows, a comprehensive assessment of the observational techniques and diagnostic tools used to characterize them, a detailed description of the best-studied cases, and a more general discussion of the statistical properties of these outflows in the local and distant universe. The remaining outstanding issues that have not yet been resolved are summarized at the end of the review to inspire new research directions.

中性原子和分子外流在近处和远处的星系中都很常见。它们在整个星系宿主范围内运行，从星系核的最内部区域到星系晕的最外层。它们携带了大量本来可以用来形成新恒星的物质。这些冷流可能对其宿主星系和环境的演化产生深远的影响。本文概述了冷流出的基本物理原理，对用于表征冷流出的观测技术和诊断工具进行了全面评估，详细描述了最佳研究案例，并对这些流出的统计特性进行了更一般的讨论在本地和遥远的宇宙中。剩余尚未解决的突出问题在综述的最后进行总结，以启发新的研究方向。