The concepts of generations and generational differences have received much attention in the academic literature, in the popular press, and among practitioners, policymakers, and politicians. Despite the continued interest, research has failed to find convincing evidence for the existence of distinct generations, commonly conceptualized as broad groupings of birth cohorts (e.g., 1980-2000) that have been influenced by a set of significant events (e.g., economic depressions) and labeled with names and qualities that supposedly reflect their defining characteristics (e.g., Millennials). Further, any differences that have been found in empirical studies, and that have been attributed to generational membership, are more likely due to age and/or contemporaneous period effects. Nonetheless, some researchers, employers, institutions, governments, and many laypeople continue to treat generations like they are a powerful and actionable phenomenon. We address these issues in two ways. First, we review the science of generations, focusing on what is known, what is not, and why the evidence points to the conclusion that generations, as popularly conceptualized, do not exist in objectively quantifiable ways. We also address the disconnect between science and practice regarding generations. Second, we explore alternate explanations for effects that are attributed to generations and review approaches that are both more theoretically sound and empirically supported, including lifespan theory and social constructionist frameworks. Finally, we address connections between assumptions made about generations and concerns about diversity, equity, and inclusion at work. Specifically, we address what has been termed generationalism, the belief that members of specific generations possess unique, stereotypic characteristics.