Mechanisms, or those biological, behavioral, social, and/or environmental processes through which an independent variable (e.g., an intervention) explains variation in one or more outcomes, were very much on my mind when reviewing the wide-ranging and excellent articles in this month’s issue of The Gerontologist. Understanding why an intervention or other key phenomena account for important outcomes for individuals, families, communities, and health care systems is essential. For example, a scientific focus on mechanisms can achieve a shared understanding across disciplines of why certain phenomena occur or help to explain various outcomes. Such understanding can contribute to the quality of theory and conceptualization. From a more applied standpoint, understanding why an intervention works is critical in the translational process, as key elements of an intervention often require modification to ensure effective “fit” and adaptation to diverse contexts. If one does not know why an intervention works, such adaptation efforts may attenuate the beneficial effects of an intervention (i.e., interfering with mechanisms of benefit/action/behavior change), thus placing the dissemination/implementation process at risk.