This book is a biblico-theological presentation of Ecclesiology, guided in particular by the ecclesiological perspectives opened up by the Second Vatican Council’s teaching on the mystery of the Church. It is the first book, ever written, that gives a full-scale theological treatise on the nature of the Church as Communion of Individual Churches. This is a book that helps to have a genuine understanding of ecclesial unity in diversity. A notable feature of this book is the clarification of the expressions ‘Particular Church’ and ‘Individual Church’, the usage of which is confusing in the documents of the Vatican II. The presentation of apostolic succession as a succession of faith along with the succession of persons is really an eye-opener. This book could be a reference work for the teachers and students of Ecclesiology. It can indeed serve as a monitor for the restoration of the full communion among the Christian Churches.