Leonardo was also the inventor of a new painting technique: the mysterious and captivating sfumato (meaning "softened" or "blurred" in Italian). Leonardo used sfumato to give the illusion of volume "without lines or borders, in the manner of smoke," he wrote.

The smoky effect was achieved through oil painting, which allows one to superimpose thin layers of translucent glaze over the work. The transition from shadow to light is very subtle, giving the delicate impression of relief, and giving Mona Lisa her lively aura!