This paper deals with regulatory experiments as a way to develop and test in practice new regulatory options as an important contribution to sustainability transitions. This is set against the background of the role of experiments in transition studies, in political science as well as a legal perspective of innovations in law. The paper presents a typology of four different types of experiments with different roles for regulation, including practical examples. A key issue is whether regulation only provides the background for technical pilots or whether regulation itself becomes the main object of an experiment. For this latter type, which is under-researched so far, the paper introduces the Regulatory Innovation Zone (RIZ) as a concept for experimenting with regulation. Originally developed in the context of Smart Grids, it can be applied to other fields. The concept is discussed with regard to the concrete design options and implementation challenges of regulatory experiments.