Amsterdam's famed Rijksmuseum on Monday began a historic restoration of Rembrandt's "The Night Watch", erecting a huge glass cage around the painting so the public can see the work carried out live.
The multi-million-euro makeover of the giant 1642 masterpiece, the survivor of a difficult history including several acts of vandalism, will also be streamed online so that people around the globe can see it.
"The Night Watch is one of the most famous paintings in the world," Rijksmuseum director Taco Dibbits told a media conference in front of the glass restoration case, alongside the research team.
"More than two and a half million people come and see it each year. It belongs to everybody who lives in the Netherlands, and the world. And we felt that the public has the right to see what happens to that painting."
Dubbed "Operation Night Watch", the project is the "largest and most comprehensive research on Rembrandt's masterpiece in history", the museum added in a statement.
"Operation Night Watch aims to preserve the painting optimally for the future and takes place in front of the public in a specially designed glass room."
Rembrandt van Rijn was commissioned by the mayor and leader of the civic guard of Amsterdam, Frans Banninck Cocq, to paint the picture of the officers and other members of the so-called "Night Watch" militia.
Experts say the groundbreaking three metre by four metre (nine feet by 13 feet) picture is the first of its kind to show such a group in motion, rather than in static poses, and features the interplay of light and shadow that the Dutch master is famed for.
- Vandal attacks -
Over the last three centuries Rembrandt's brooding painting has endured travails including an escape from the Nazis, losing large chunks from each side during a move, and three attacks by vandals.
The last major restoration work was carried out 40 years ago, after a mentally ill man slashed it with a knife, and it is now housed in its own special room in the Rijksmuseum.
But experts have recently noticed changes to the painting, with a white haze appearing on some parts, especially in the area around the knife damage, where it is bleaching out the figure of a small dog.
The museum wants to "understand how the changes are happening and the best way to restore it", Dibbits said when he unveiled the project in October.
Experts will examine the painting using high-resolution photography and computer analysis of every layer including varnish, paint and canvas before deciding on the best restoration techniques.
The work will then take place in a glass case designed by French architect Jean-Michel Wilmotte, who was behind revamps of both the Rijksmuseum and the Louvre gallery in Paris.
"This research and restoration will be carried out with the world watching... so that everyone in the world, no matter where they are, can see," Dibbits added.