Ion processes are a key driver of chemistry in a wide variety of natural dilute environments such as the ionosphere of Earth, the atmosphere of solar system planets, and satellites and interstellar clouds. They also play a role in low-temperature plasmas that are commonly encountered in industrial settings. Uniform supersonic flows have proved to be pivotal in gaining insights into the kinetics of ionic processes. In more than three decades, a variety of ion-molecule reactions has been investigated with the CRESU (French acronym standing for Kinetics of Reactions with Uniform Supersonic Flows) method. They include bimolecular and termolecular reactions and often depart from predictions made by simple empirical models. Neglected in the 90s for the benefit of the study of less predictable radical-neutral reactions, the exploration of ion-molecule reactive collisions has seen a recent revival. It has been in particular stimulated by the discovery of molecular anions in astrophysical environments for which the formation and destruction processes remain elusive, mostly due to the lack of kinetic and branching ratio data. Despite the growing sophistication of competing methods which include crossed beams or cooled ion traps, uniform supersonic flows continue to be a method of choice, one of the rare techniques to provide rate coefficients obtained under well-controlled thermalized conditions over a wide range of low temperatures. Uniform supersonic flows turn out to be well suited for heavy neutral co-reactants. Some challenges remain and call for new directions of action. In a last section, the most promising routes and the limits of the method are outlined. The extension of the method to the study of dissociative recombination sounds perilous, and state-selective chemistry with ions could only marginally benefit from the CRESU. From a technical point of view, the implementation of isomer-specific detection schemes could, however, greatly expand the scope of ion-molecule reaction studies. In tight connection with planetary sciences, ion-induced nucleation appears to be a topic within reach today using the CRESU technique. Further development of the approach will contribute to validate approximate treatments and push further the knowledge of ion-molecule reactions at low temperatures. © 2022 by World Scientific Publishing Europe Ltd.