The panel is poplar wood, approximately 30 by 21 inches. It has been analyzed with modern imaging technology — infrared reflectography, multispectral imaging — that has revealed underdrawings and multiple stages of revision. Leonardo made changes to the composition during the painting process; earlier states of the composition show that the landscape and some figure details were adjusted.
The painting that Vincenzo Peruggia hid in a trunk for twenty-eight months was, by the consensus of art history, one of the greatest technical achievements in the history of Western painting and a central document in the development of naturalistic portraiture. That Peruggia understood it primarily as a potentially valuable object to be sold, rather than as an artwork, was not a reflection of his personal failings alone. It was a reflection of the gap between the world of art expertise and the world of an Italian immigrant laborer in early twentieth-century Paris.
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## After Peruggia: The Painting’s Subsequent History
The Mona Lisa’s story did not end with its recovery in 1913. The decades that followed added chapters to its biography that deepened its global celebrity.
In 1956, a visitor to the Louvre threw acid at the lower portion of the painting, damaging the paint surface in the lower area of the composition. Later the same year, another visitor threw a rock at it, chipping the elbow area. These attacks accelerated the installation of protective measures that had been discussed but not fully implemented.
After that point, the painting began to be displayed with increasingly robust physical barriers. It was eventually moved to a dedicated display space and placed behind bulletproof glass — the standard of its current presentation.