The famous smile on Leonardo Da Vinci's Mona Lisa could be because she is pregnant or had just had a baby, research suggests.
The scans can look beneath old paint and varnish
Canadian scientists used laser and infrared scans to produce a 3D image of the painting.
This allowed details beneath layers of paint to be seen - including a gauzy dress then associated with pregnant or new mothers.
It also showed the 500-year-old picture was in good condition.
The scans, using a resolution 10 times finer than a human hair, did reveal some warping to the wooden back of the painting.
The team from National Research Council of Canada (NRC) were given rare access to the painting at its home in the Louvre Museum in Paris.
It said other details obscured by darkened paint and varnish included the hair originally being in a bun and a slightly different posture, as well as the gauze dress.
"This type of gauze dress ... was typical of the kind worn in early 16th Century Italy by women who were pregnant or who had just given birth," said Bruno Mottin of the French Museums' Center for Research and Restoration.
"This is something that had never been seen up to now because the painting was always judged to be dark and difficult to examine."
The woman herself has been identified as the wife of Florentine businessman Francesco del Giocondo.
Da Vinci was commissioned to paint the portrait between 1503 and 1506 but kept it and may have altered it several times.
While some questions about the painting may have been answered, other mysteries remain - particularly around how the image was created.
The method of Da Vinci's sfumato - or smoky - painting technique continues to elude experts.
John Taylor, from the NRC, said: "It's extremely thinly painted and extremely flat, and yet the details of the curls of hair, for example, are extremely distinct.
"So, the technique is unlike anything we've ever seen before".