The classical phase of pietism, which lasted in Germany from 1670 through 1780, constitutes a vital chapter in the history of Christianity. Pietists perfected a particular organizational form, the
ecclesia - the little church within the Church. They then used this form to initiate many innovations in missions, social service, education, and ecumenical activity.
Studies in Classical Pietism carefully analyzes the
ecclesiola and displays its power in the work of six pietist leaders beginning with Philip Jakob Spener.