New scientific research into one of Leonardo da Vinci’s most celebrated works has revealed a hidden composition and fingerprint marks that were once invisible to the naked eye.

Larry Keith, head of conservation at the National Gallery, believes the discoveries “give new insight into how da Vinci was thinking“.

As a notoriously slow artist, Leonardo painted ‘The Virgin of the Rocks’ in two campaigns in 1491-99 and later in 1506-08. The panel painting depicts the Virgin, accompanied by an Angel and the infant Saint John the Baptist, adoring the Christ Child. Initially intended as an altarpiece for a church in Milan, the painting now hangs in the National Gallery.

Experts at the National Gallery used macro X-ray fluorescence maps and infrared and hyperspectral imaging to highlight the zinc in any drawing material in the painting. The investigation uncovered a completely different composition beneath the surface of ‘The Virgin of the Rocks’.

An initial investigation in 2005 discovered a change in the Virgin’s position, but any alterations to the other figures were still unclear.

“This time we can see an angel and a Christ child we couldn’t really see before. We could see a few lines but we couldn’t see what it was [in 2005],” explained Marika Spring, the gallery’s head of science.

New technology now shows that the angel and infant Christ were originally positioned higher up, with the angel facing out and looking down. Leonardo’s reasoning behind making these dramatic changes remains unknown.

According to Keith, these adjustments fit “into a wider narrative of how we understand him [Leonardo] as an artist who was always changing, adjusting and revising“.

Later this year, Leonardo’s renowned masterpiece will take centre stage at an “immersive” exhibition held at the National Gallery. It will highlight the painting’s hidden secrets “and the inventive mind that created it“.

Caroline Campbell, the gallery’s director of collections, remarked that “much of our research takes place in closed studios, laboratories and libraries,” and the upcoming exhibition will offer the public a chance “to explore and engage with what we have found”.

For the first time visitors can also see the delicate fingerprints left on the surface of the painting, made visible by high resolution photography. Perhaps by a workshop assistant or even Leonardo himself, fingers were delicately pressed into the wet paint to smooth down the material.

Managing director Richard Slaney added: “We work at the nexus between technology and art … applying the latest cutting-edge technologies in the pursuit of incredible storytelling.”

Leonardo: Experience a Masterpiece will run from 9 November to 12 January at the National Gallery in London.