Leonardo da Vinci, A wooden machine for the excavation of a canal (c. 1503) Codex Atlanticus. Credit: Leonardotheka.

For more than four centuries, Leonardo da Vinci’s largest surviving body of notes has remained divided and scattered. In the late 1500s, the sculptor Pompeo Leoni took apart Leonardo’s manuscripts, cut pages, rearranged folios and divided the material into separate albums. Technical and scientific writings went one way. Figurative drawings, anatomical studies, landscapes and natural-history sketches went another.

To Leoni, who perhaps was flexing his organization muscles, separating da Vinci’s life work into neat and tidy boxes probably made sense. The famed polymath himself, however, might have disagreed, seeing how his body of work was built on the unity of art and science.

Now, for the first time since that intervention, two of the most important surviving collections of Leonardo’s writings and drawings have been brought back together — not physically, but digitally.

The Museo Galileo in Florence has launched Leonardotheka, an online platform that reunites the 1,119 sheets of the Codex Atlanticus, held by the Veneranda Biblioteca Ambrosiana in Milan, with roughly 550 Leonardo sheets in the Royal Collection at Windsor.

Together, they form what the museum and its partners describe as the world’s most extensive digital resource devoted to Leonardo’s manuscripts.

The project, developed over 10 years with the Royal Collection Trust, the Biblioteca Leonardiana in Vinci and other partners, gives scholars and the public a new way to search, compare and reconstruct Leonardo’s work across about 3,500 manuscript pages.

Reassembling da Vinci’s Entire Body of Work Leonardo da Vinci, Head of Leda (c. 1505-1508), RCIN 912516r. Credit: Royal Collection Enterprises Ltd 2026 | Royal Collection Trust. Studies for the painting Leda and the Swan, now lost.

Da Vinci, born in 1452, filled thousands of pages with notes, diagrams, observations and designs before his death in 1519. His manuscripts range from diagrams of flying machines and musical instruments to detailed studies of anatomy, optics, water dynamics, architecture, weapons, plants and horses. And that’s only mentioning what manuscripts survived to this day.

This extensive range is precisely the point. To Leonardo, scientific observation, invention and art fed one another.

After Leonardo died, his final pupil, Francesco Melzi, inherited the manuscripts. They later passed to Leoni, who dismantled notebooks and loose sheets and reorganized them into two albums. The larger, more technical album became the Codex Atlanticus. In 1637, Count Galeazzo Arconati donated it to the Ambrosiana in Milan.

Leonardo da Vinci, studies of a flying machine, c. 1490-1495 from Codex Atlanticus, f. 846v. Credit: Veneranda Biblioteca Ambrosiana.

The other album, containing many of the figurative works, reached England in the 1620s and entered the Royal Collection around 1670, probably as a gift to King Charles II.

Leonardo da Vinci, Mechanism for drawing water-driven metal bars for cannon (c. 1490-1515), Codex Atlanticus, f. 10r. Credit: Veneranda Biblioteca Ambrosiana Leonardo da Vinci, Machines for raising water (c. 1480-1482), Codex Atlanticus, f. 26v. Credit: Veneranda Biblioteca Ambrosiana

The split shaped how generations encountered Leonardo. It also reinforced a misleading divide between Leonardo the artist and Leonardo the engineer. Leonardotheka now merges all this work into one unified, digitized, easily browsable/searchable database.

“Leonardotheka is a tool that offers scholars worldwide unprecedented opportunities to explore the vast and invaluable wealth of information contained within Leonardo da Vinci’s manuscripts,” said Professor Paolo Galluzzi, president emeritus of Museo Galileo.

The platform “marks the beginning of a new and highly promising era of research into the artistic, scientific, and literary legacy of the genius of Vinci,” Galluzzi added.

A Digital Restoration Leonardo da Vinci, Cats, Lions and a Dragon (c. 1517-1518), RCIN 912363r. Credit: Royal Collection Enterprises Ltd 2026 | Royal Collection Trust Leonardo da Vinci, Fetus in the Womb, drawings and notes on reproduction (c. 1511), RCIN 919102r. Credit: Royal Collection Enterprises Ltd 2026 | Royal Collection Trust

Some of the pages from the newly stitched-together catalog have been digitally reconstructed. That’s perhaps the strongest output to come out of this initiative.

Researchers have reconstructed at least 50 pages of Leonardo’s old manuscripts by matching fragments from Windsor with sheets in the Codex Atlanticus. They examined page dimensions, paper preparation, writing materials and watermarks with the flair of a forensic detective.

One reconstruction reunites a drawing of a horse with Leonardo’s written reflection on the Regisole, a classical equestrian monument in Pavia. Scholars believe the pairing may capture the moment Leonardo settled on the final sketch for the horse intended for the enormous, never-completed Francesco Sforza monument.

Leonardo da Vinci, Studies of Horses (c. 1490), RCIN 912321r. Credit: Royal Collection Enterprises Ltd 2026 | Royal Collection Trust

At the end of the day, Leonardo’s notebooks were not polished books. They were more akin to workspaces and drafts. Da Vinci argued with himself on paper. He moved between image and text. He tested forms, mechanisms and proportions as he thought, rather freestyle.

The platform also lets users filter the material by content, technique and other traits, while connecting pages to scholarly resources. In practice, it turns a scattered archive into a navigable research environment.

Beyond Leonardo Leonardo da Vinci, Machine for digging canals (c. 1503), Codex Atlanticus, f. 4r. Credit: Veneranda Biblioteca Ambrosiana

The launch also speaks to a larger question facing museums and libraries: who should control the digital future of cultural heritage?

Roberto Ferrari, executive director of Museo Galileo, said Leonardotheka “sets a compelling precedent for how cultural institutions can and must retain intellectual ownership of their digital endeavors, resisting the temptation to delegate such responsibilities to commercial platforms,” according to Artnet.

Rearrangement: Codex Atlanticus, f. 399r + RCIN 912345r. Credit: Royal Collection Enterprises Ltd 2026 | Royal Collection Trust. Recomposition: Codex Atlanticus, f. 878v + RCIN 912464r, RCIN 912438r, RCIN 912460r. Credit: Veneranda Biblioteca Ambrosiana © Royal Collection Enterprises Ltd 2026 | Royal Collection Trust Codex Atlanticus, f. 86r. Credit: Veneranda Biblioteca Ambrosiana

“In an age of rapidly evolving artificial intelligence, this project reminds us that the true value of digital humanities lies in the willingness of scholarly institutions to assume direct responsibility for shaping the tools through which our shared heritage is explored and understood,” Ferrari added.

Fabio Cassese, the Italian ambassador to the U.K., said that “the importance of Leonardo transcends national borders,” he said, according to RTE. “He belongs not only to Italy, but to the cultural and scientific heritage of humanity as a whole.”

Four hundred years after Leonardo’s pages were cut apart, the reunion is still incomplete in the material sense. The sheets remain in Milan and Windsor. But online, their old conversations can begin again.