The Multiple-Resource Theory (MRT) of Attention has significantly advanced our understanding of cognitive processing by proposing that humans allocate attentional resources across multiple modalities and processors. Since its origin, the theory has undergone numerous adaptations and expansions, aligning with emerging empirical evidence and technological advancements. This overview therefore traces the evolution of the MRT, highlights key developments, critiques, and contemporary perspectives, and underscores the importance of ergonomic considerations in optimizing human performance across various settings.