This important book charts the historical development of citizen science, from its earliest days with amateur individuals working on their own, to the modern incarnation which often sees large numbers of people cooperating on environmental or health projects. It will help project designers understand the heritage of citizen science, including the best way to avoid previous mistakes, and how to ensure results which are both reliable and informative. It also encourages individuals to participate and to think beyond the simple collection of data; how can each of us contribute? As scientists themselves, the authors have a clear understanding of the need for reliable, rather than anecdotal, information about the ups and downs of citizen science projects. Both have been involved in such initiatives, from individual data collection to testing identification keys for practical use by the public. Many readers will be surprised at the breadth of citizen science and will discover the ability to undertake their own investigations. This book will be of great interest to anyone participating in or organising collaborative citizen science projects.