Twenty-five years ago, Nobu Kiyotaki and Randy Wright (1989) published a paper that introduced a new approach, based on search theory, into monetary economics. In this approach, agents in the model trade with each other, and not simply against their budget lines. This allows one to start asking how they trade - using barter, commodity or fiat money, secured or unsecured credit, etc. Over the last twenty-five years much progress has been made in the area, applying and extending the original model on many dimensions. This conference provides an opportunity to look back at what has been done, and to look forward to where monetary economics will go in the future.