What's the role played by the invisible in our lives? At what level can it be perceived when explored in theatre-making? Having as its focus the acting processes carried out by Peter Brook and his actors, this book examines many aspects of their practical work - from actor training seen as "poiesis" to the production of the "present moment" - and in doing so, it tries to recognize the nuances and subtle qualities generated by the invisible produced by them. However, the core of this investigation is that of trying to capture the invisible not as a vague sensation but in its dynamic and powerful manifestation.