A French scientist discovered a secret behind one of Leonardo Da Vinci's most famous paintings. 

"The Lady With an Ermine," which was created around 1490, was painted three different times. 

French scientist Pascal Cotte used lighting technology called the Layer Amplification Method to see what's beneath the top layer of oil paint on the walnut board.

"The LAM technique gives us the capability to peel the painting like an onion, removing the surface to see what's happening inside and behind the different layers of paint," Cotte explains to BBC

Cotte spent three years looking beneath the painting, discovering the ermine that the woman pictured is cradling in her arms wasn't always part of the piece. 

He unveiled three versions of the painting. The first was of just the woman, the second was the woman with a very skinny ermine, and the last is the one that became famous - a woman cradling a full-looking ermine. 

Da Vinci experts are calling the painting "thrilling" and are intrigued about the new history behind the famous piece, reports BBC.

The scientist explains what this discovery shows:

"It tells us a lot more about the way Leonardo's mind worked when he was doing a painting. We know that he fiddled around a good deal at the beginning, but now we know that he kept fiddling around all the time and it helps explain why he had so much difficulty finishing paintings."

The original "The Lady With The Ermine" portrait was bought by Polish Prince Adam Jerzy Czartoryski in Italy and incorporated into The Czartoryski family collections in 1800. The painting belongs to the Czartoryski Museum in Krakow, Poland. However, due to renovations, the piece is temporarily exhibited at the Wawel's Krakow Royal Castle in an upstairs room of the castle's western wing.