An apprenticeship is a position by which one individual learns a skill through hands-on, practical experience under the tutelage of another who excels at such skills. Leonardo was apprenticed to Andrea del Verrocchio in Florence, where he learned a range of techniques—from painting and sculpture to mechanics and theatrical design. This hands-on training reflected the Renaissance workshop tradition and became the foundation for Leonardo’s interdisciplinary thinking. His early contributions to collaborative works during this period reveal his precocious skill and curiosity.

Chiaroscuro is the use of strong contrasts between light and dark to create a sense of volume and three-dimensionality. Leonardo mastered and advanced this technique in his paintings, particularly in The Virgin of the Rocks and The Last Supper. It allowed him to create lifelike figures and a dramatic, atmospheric effect that contributed to the emotional realism of his work.

One of Leonardo’s most famous notebooks, the Codex Leicester contains his studies of water, geology, astronomy, and natural philosophy. Purchased by Bill Gates in 1994, the codex exemplifies Leonardo’s approach to knowledge as a blend of empirical observation, imaginative theory, and visual expression. His notes in this volume challenged conventional beliefs about topics like fossils and the source of springs.

While in Milan, Leonardo was often employed not as a painter but as a designer of elaborate court spectacles. These events, known as court entertainments, combined music, mechanics, costumes, and theatrical illusions. They gave Leonardo deadlines and creative outlets and foreshadowed his later inventions, as his devices for pageants often sparked deeper scientific inquiry.

Dissection is the process of separating a specimen into pieces to expose the parts, often for scientific examination purposes. Leonardo’s dissections, conducted in hospitals across Italy, were groundbreaking for their time. He produced more than 240 detailed anatomical drawings, including studies of the heart, brain, vascular system, and internal organs. His approach combined artistic observation with engineering precision, though the results were not widely known until centuries later.

Engineering is a branch of science and technology that focuses on designing, building, and using engines or machines to solve problems. Leonardo frequently emphasized his capabilities as an engineer in job applications, proposing designs for bridges, tanks, canals, and city planning. Though few of his engineering projects were completed, his notebooks reveal an advanced understanding of mechanical systems and hydrodynamics. His visual approach to design—exploded diagrams, layered systems, and analogies to the human body—helped define a modern conception of engineering.

Leonardo spent decades focused on “flying machines,” studying bird flight and trying to design machines that would allow humans to fly. He made over 500 sketches and theoretical notes, ranging from flapping ornithopters to gliders. Though none were successful, his observations anticipated principles later formalized in aerodynamics, making his flight studies a major part of his scientific legacy.

As a central figure of the Renaissance, Leonardo embodied the values of humanism: a belief in the potential of human intellect, sensory experience, and artistic expression. Isaacson argues that Leonardo’s life and work reflect a celebration of the human mind’s capacity to explore and understand the world through multiple lenses—artistic, scientific, and philosophical.

Born out of wedlock, Leonardo was considered an illegitimate heir to his father. He was barred from following his father into the notary profession and excluded from formal university training as a result. This marginal status ironically gave him intellectual freedom, allowing him to pursue self-directed study and work across disciplines. Isaacson suggests that Leonardo’s outsider identity informed both his psychological development and his boundary-defying creativity.

Leonardo’s notebooks, which number over 7,200 pages, reflect the Renaissance tradition of the zibaldone, or personal miscellany. These books contain sketches, scientific musings, anatomical diagrams, jokes, engineering plans, and philosophical reflections. Isaacson uses these notebooks as both source and structure for his biography, treating them as a window into Leonardo’s mind and method.

In art, perspective refers to the technique artists use to depict objects in their projects. Leonardo mastered both linear and atmospheric perspective, using them to guide the viewer’s eye and create depth. In The Last Supper, he used a vanishing point at Christ’s head to create spatial harmony. He also used atmospheric effects—blurring backgrounds and shifting colors—to enhance realism and visual cohesion.

Sfumato, meaning “smoky” in Italian, refers to Leonardo’s signature technique of softening edges and blending tones to create a realistic, hazy transition between colors and forms. Most famously seen in the Mona Lisa, this method reflects Leonardo’s studies in optics and his desire to depict the complexity of human emotion and facial movement.