Leonardo da Vinci’s Codex Atlanticus, the largest collection of his drawings and writings, has been fully assembled for the first time in 400 years. Previously split into two volumes, one held in Milan and the other in Windsor, the complete codex offers a comprehensive view of da Vinci’s diverse interests and innovations. The unification allows researchers and the public to study the entirety of the work as originally conceived. The codex contains over 500 pages of sketches and notes covering topics from engineering and anatomy to architecture and art. This historic reunion provides invaluable insight into the mind of the Renaissance master. The project involved careful coordination between the Ambrosiana Library in Milan and the Royal Collection Trust in Windsor.