In nature, living organisms have the ability to respond to environmental factors, which cause them to behave differently or take on different forms. At the microscopic level, external stimuli regulate feedback loops and modulate enzymatic reactions within cells to affect biological changes. Taking inspiration from nature, scientists have been working on artificial catalytic systems that could be tuned reversibly by external stimuli. In such switchable systems, a catalyst could be toggled on/off or oscillate between different catalytic states to achieve orthogonal reactivity. In this section, redox, chemo-, and photo switching methods will be discussed. Because some comprehensive reviews have been already published on this topic, we will focus primarily on the switching mechanisms and general catalyst design concepts.