This lecture introduces the concept of Implementation Research (IR) focusing on how to adopt interventions, instruments, or treatments in controlled conditions and make them available to those in need, ensuring system capacity for sustainability. It covers the importance of IR for infectious diseases, key phases in IR, related research, characteristics of IR, strategies design, different types of implementation strategies, research questions, and effectiveness of implementation. The lecture also discusses the distinction between intervention efficacy and implementation effectiveness, as well as the outcomes of implementation efforts such as acceptability, adoption, feasibility, and sustainability.