This chapter offers an introduction to the book. It defines regulation, distinguishing it from other concepts such as governance. We define regulation as ‘intentional, organised attempts to manage or control risk or the behaviours of a different party through the exercise of authority, usually through the use of mechanisms of standard-setting, monitoring and information-gathering and behaviour modification to address a collective tension or problem’. The Introduction reflects upon the most important changes in regulation in the last two decades and the growing relevance of regulation in society. The chapter explains significant changes in the practice and context of regulation that have occurred since the first editions was published.