Abstract: Understandable robots (aka explainable, intelligible or predictable robots) is a subfield in Human-Robot Interaction that investigates how robots should be designed so that humans understand them, in the sense of being able to successfully interact with them. As interaction, robots' capabilities and perceptions , and humans' discernment of robots are ever-changing, the concept of understandability is a concept of adaptation, and continuous and multifaceted change. In this presentation we will cover, our past and ongoing research in this field, including research design methods, aspects to determine the human's behavior, and strategies that help the robot to support the understandability process.