The Mona Lisa is the most visited painting in the world. In any given year before the Louvre reduced crowd capacity, more than ten million people passed through the Grande Galerie to stand in front of it, often for just a few seconds before being jostled by the next visitor. The painting is twenty-one inches wide. Most visitors are surprised by how small it is, and by how far away they are kept from it. But the painting's power is not in its size. It is in the quality of attention Leonardo da Vinci brought to every square inch of its surface, which remains unlike anything painted before or since.
Leonardo was not just a painter. He was a sculptor, architect, musician, mathematician, engineer, inventor, anatomist, geologist, botanist, cartographer, and writer. He filled over 7,000 pages of notebooks with drawings, observations, and ideas, many of which anticipated technologies not realized until centuries after his death: the helicopter, the armored vehicle, the solar power concentrator, the double hull ship. He studied the anatomy of the human body by dissecting over thirty corpses. He studied the flight of birds to design flying machines. He observed the behavior of water and catalogued it in drawings of breathtaking precision.
This profile explores how Leonardo's art and science fed each other, why he left so many works unfinished, and what he actually contributed to painting that makes his surviving work so different from everything around it.
Early Life in Florence: A Bastard Son's Extraordinary Education
Leonardo di ser Piero da Vinci was born on April 15, 1452, in the small Tuscan town of Vinci. He was the illegitimate son of a Florentine notary, Ser Piero da Vinci, and a local woman named Caterina. Being born out of wedlock closed certain professional doors to him: he could not follow his father into the notarial profession, which required legitimate birth. But it also freed him from certain expectations. His father recognized his talent and, around 1466, apprenticed the fourteen-year-old Leonardo to the workshop of Andrea del Verrocchio in Florence, one of the most respected artists and craftsmen in the city.
Verrocchio's workshop was an extraordinary training ground. Verrocchio worked in painting, sculpture, goldsmithing, and engineering, and his apprentices learned all of these disciplines. Leonardo spent about ten years in the workshop, absorbing Florentine Renaissance technique: linear perspective, anatomical proportion, the idealized human figure derived from classical Greek and Roman sources. But he quickly outpaced his master. According to the art historian Giorgio Vasari, when Verrocchio saw that Leonardo had painted an angel in their collaborative work "The Baptism of Christ" (c.1472-75) so much more beautifully than his own figures, he never painted again.
Florence under Lorenzo de' Medici was the intellectual and artistic center of Europe, and Leonardo absorbed its culture intensely. He read widely, attended lectures in philosophy and natural science, and became a regular presence at the court of Lorenzo the Magnificent. But Florence could not contain his ambition. In 1482, at age thirty, he wrote a long letter to Ludovico Sforza, the ruler of Milan, listing his abilities: he could design portable bridges, armored vehicles, cannons, and other military machines; he could design and build public buildings; and, almost as an afterthought at the end of the letter, he mentioned that he could also paint.
Milan and the Last Supper
Leonardo spent nearly eighteen years in Milan under Sforza's patronage. During this period, he began the notebooks that would eventually fill thousands of pages with scientific observations, mechanical drawings, and artistic studies. He also produced his most ambitious surviving painting: "The Last Supper" (1495-98), painted directly on the refectory wall of the convent of Santa Maria delle Grazie.
"The Last Supper" is not a fresco. Leonardo used a technique of his own devising, applying tempera and oil directly onto a dry plaster wall rather than into wet plaster as fresco technique required. He chose this approach because fresco required working quickly before the plaster dried, and Leonardo was constitutionally incapable of working quickly. He would sometimes spend an entire day staring at the wall before making a single mark. The result of his unconventional technique was a painting that began deteriorating within twenty years of its completion. It has survived wars, floods, and centuries of neglect in a compromised state. And yet it remains one of the most powerful paintings in existence.
Leonardo da Vinci, "The Last Supper" (1495-98), tempera on gesso, pitch, and mastic, 460 x 880 cm. Santa Maria delle Grazie, Milan. The deterioration visible in the painting began within decades of its completion, due to Leonardo's experimental non-fresco technique. Image: Public domain, via Wikimedia Commons
What makes "The Last Supper" so powerful is its psychological organization. Leonardo chose to depict the moment immediately after Christ says "One of you will betray me." The twelve apostles react in groups of three, each cluster showing a different emotional response: shock, denial, grief, anger, conspiracy. The psychological range is astonishing. Leonardo prepared for the painting by studying the faces and bodies of real people throughout Milan, looking for models who embodied the specific emotional qualities he needed. He reportedly told Sforza that he had been unable to find a sufficiently villainous face for Judas, but might use the face of the Prior of the convent, who had been pestering him to work faster.
The Mona Lisa and the Invention of Sfumato
Leonardo's most famous painting was begun around 1503-06 in Florence and probably continued until around 1517, making it a work of more than a decade. The subject is thought to be Lisa Gherardini, wife of a Florentine merchant named Francesco del Giocondo. The painting is also known as "La Gioconda" in Italian, or "La Joconde" in French.
The technique that defines the Mona Lisa and much of Leonardo's mature work is sfumato, from the Italian word for "smoke." Sfumato is the technique of blending tones so gradually that there are no visible edges between them, creating the illusion that forms emerge from shadow rather than being defined by line. Look closely at the corners of the Mona Lisa's mouth or eyes and you will find no clear boundary where skin ends and shadow begins. The forms dissolve into each other like smoke into air. This creates an ambiguity of expression that has fascinated viewers for five centuries: the smile shifts depending on where your eye focuses, a psychological effect that Leonardo engineered deliberately.
To achieve sfumato, Leonardo applied oil paint in dozens of extraordinarily thin layers, sometimes as thin as a single micron. Studies using X-ray fluorescence have found no brushstrokes at any scale in parts of the Mona Lisa's face: the layers are so thin and so smoothly applied that no instrument has yet detected how they were put down. The technique may have involved Leonardo applying paint with his fingertips rather than a brush. This kind of obsessive technical perfection explains why Leonardo left many paintings unfinished. He set himself standards that were almost impossible to meet, and the process of continuous revision and refinement could go on indefinitely.
Leonardo da Vinci, "The Vitruvian Man" (c.1490), pen and ink on paper, 34.4 x 24.5 cm. Gallerie dell'Accademia, Venice. Based on the writings of the ancient Roman architect Vitruvius, this drawing explores the mathematical proportions of the ideal human body. Image: Public domain, via Wikimedia Commons
The Notebooks: Art as Scientific Investigation
Leonardo kept notebooks throughout his working life, writing in mirror script that could only be read by holding the pages up to a glass. About 7,000 pages survive, out of an estimated 13,000 he produced. The content ranges from anatomical drawings made from dissected cadavers, to designs for military machines, to studies of water flow and rock formation, to drawings of plants, horses, and human faces, to musical instruments and theatrical designs.
The anatomical drawings are particularly extraordinary. Leonardo collaborated with the physician Marcantonio della Torre at the University of Pavia and dissected more than thirty human bodies, making drawings of the skeleton, muscles, organs, and nervous system that were not surpassed in accuracy until the 19th century. His drawing of the human fetus in the womb (c.1511) shows the baby in its correct curled position with anatomical precision that was unknown to the medicine of his time.
For Leonardo, there was no meaningful distinction between art and science. Both were methods of understanding how the world worked. A drawing of a dissected arm helped him paint arms more convincingly. A study of water in motion helped him represent flowing hair and drapery in painting. The notebooks were not a secondary interest alongside his art; they were the same activity expressed in different forms. This is what makes Leonardo the defining figure of the Renaissance ideal of the complete human being, the "uomo universale" who seeks knowledge in every direction simultaneously.
Final Thoughts
Leonardo da Vinci died on May 2, 1519, in Amboise, France, at the age of 67, while serving as court painter to King Francis I of France. According to Giorgio Vasari, the king was present at his death, holding Leonardo's head in his arms. Whether or not the story is literally true, it captures something real: in his final years, Leonardo was cherished not primarily as a painter but as a mind, as the greatest intellect of the age.
He left only about fifteen surviving paintings. He started far more and abandoned most of them. His legacy is frustrating in this sense: we are left with fragments of what he intended to produce. But what survives is more than enough to establish why his reputation has held for five centuries. The sfumato technique, the psychological depth of his portraits, and the integration of scientific observation into artistic practice fundamentally changed what painting could be. Every artist who has tried to paint with precision and feeling simultaneously has worked in a tradition that Leonardo helped create.
For a broader look at the movement that shaped Leonardo, read the full guide to Renaissance Art: Perspective, Humanism, and the Birth of Modern Art. For a guide on what techniques like sfumato share with other approaches to representing depth and form, see Drawing Fundamentals: Line, Shade, Form, and Perspective. What aspect of Leonardo's work fascinates you most: the paintings, the scientific drawings, or something else? Tell us in the comments.
