This new edition of Leonardo Da Vinci's Codex Leicester is the most comprehensive scholarly edition of any of Leonardo's manuscripts. It contains a high-quality facsimile reproduction of the Codex, a new transcription and translation, accompanied by a paraphrase in modern language and a page-by-page commentary, and a series of interpretative essays. This important endeavour introduces important new research into the interpretation of the texts and images, on the setting of Leonardo's ideas in the context of ancient and medieval theories, and above all into the notable fortunes of the Codex within the sciences of astronomy, water, and the history of the earth, opening a new field of research into the impact of Leonardo as a scientist after his death.