How much natural light is there in a room? And what kind of light? Two deceptively simple questions architects usually have no answers to, not even when asked about their own works. Regardless of whether the deficiency is in the right vocabulary, verification tools or unfamiliarity, it is a symptom of a far more serious problem: natural light is absent from design practice. In the technical field, this almost always amounts to the formal compliance with some dimensional reference, so that natural lighting eventually occurs more as a random result than as a technically designed and controlled phenomenon. Anyone who is searching for a practical method to design it does not know where to look. This manual intends to fill a disciplinary void, starting from the basic assumption that light depends on geometry: by designing the latter, one also controls the first, but only provided one understands the mechanisms of this consequentiality. In this book, which includes a wealth of photographs and diagrams, the author shares his experience as a designer, consultant and trainer in this field. The proposed method, whose structure is reflected in the book, investigates and sorts out the basic tools and terminology of the two major possible approaches: the view/composition one and the performance/measurement one, exposing their opportunities, criticalities and interactions. Anyone looking for their zenith will find here a reference for recapturing light and integrating it into his work by means of a streamlined and immediately effective toolbox.