Leonardo da Vinci was the embodiment of the Renaissance ideal of the universal man, the first artist to attain complete mastery of all branches of art. He was a painter, sculptor, architect and engineer besides being a scholar in the natural sciences, medicine and philosophy. He was born on the 15th of April, 1452 as an illegitimate son of the notary Ser Piero di Antonio da Vinci and the peasant woman Caterina in a small town Vinci, near Empoli, Tuscany. First four years of his life he spent in a small village near Vinci with his mother. Since 1457 he lived in his father's family, which soon moved to Florence. At the age of 15 he became an apprentice of the Florentine painter and sculptor Andrea del Verrocchio and although in 1472 he entered the San Luca guild of painters in Florence, which would indicate that he had attained a degree of professional independence, he remained with Andrea del Verrocchio until 1480. His first known work, which he painted as an assistant, is the angel, kneeling on the left of the Verrocchio's picture The Baptism of Christ (c.1472-1475). Verrocchio, it is said, was so impressed by the implications of his pupil's genius that he gave up painting. Another work of this period The Annunciation (c.1472-1475) was attributed to Leonardo, but probably not all the picture was painted by him. However, it is generally accepted that the overall composition, the figure of the angel and the landscape are his. There are several other survived works from this period, such as Madonna with the Carnation (c.1475), Madonna Benois (c.1475-1478), Portrait of Ginevra de'Benci (c.1478-1480). Leonardo received a commission to paint an altar piece St. Hieronymus (c.1480-1482), which was never finished, and for the church in San Donato a Scopeto to create a large panel Adoration of the Magi (1481-1482), which was not finished either. Unfortunately, it was to be repeated with many of his works, many of them were never finished. In 1482 Leonardo moved to Milan in hope to obtain the patronage of the ruler of the city Ludovico Sforza, also known as Ludovico Moro for his dark coloring. Leonardo offered his services as a military engineer, sculptor and painter. In 1483 he was commissioned to make a large altar piece The Virgin of the Rocks (1482-1486) for the Franciscan Confraternity in the Church of S. Francesco Grande. Another version of this picture was created later. Being the court painter, sculptor and engineer he created Portrait of Cecilia Gallerani (Lady with an Ermine) (c.1490), Portrait of an Unknown Woman (La Belle Ferroniere) (c.1490), several small Madonnas, such as Madonna Litta (c. 1490), worked on the equestrian statue of Francesco Sforza (father of Ludovico Moro), which was created as a huge clay model of the horse, but the project was never cast in bronze. Leonardo painted The Last Supper (c.1495-1498) for the refectory of the Dominican Monastery Santa Maria delle Grazie, which is considered the first work of High Renaissance. His representation of the theme has become the epitome of all Last Supper compositions. Unfortunately, he experimented with the paint and this led to the damage of the fresco, the paint  began to crumble almost after the fresco was finished. See one of the contemporary copies. In the mid to late 1480s, when Leonardo was attempting to establish himself as a court artist, he seemed to have started on his huge range of scientific researches, which included botany, anatomy, medicine, architecture, military engineering, geography etc. We know about his studies by the enormous amount of his drawings which were left. He was writing the Treatise on Painting, a collection of practical and theoretical instructions for painters, all his life. In 1499, after the defeat of Ludovico Sforza by French, Leonardo left Milan. After the short travels to Mantua and Venice he returned to Florence. There he was working on a commission for the Servite monastery, which probably was Virgin and Child with St. Anne (c.1502-1516). In 1502 he was employed by General Cesare Borgia as an architect and military engineer, with whom he traveled, mainly in Central Italy, studying terrain and preparing maps for Borgia's future military campaigns. Also at that time Madonna of the Yarnwinder (1501) was created . n 1503 Leonardo returned to Florence again and, in response to a commission from Francesco del Giocondo, started on a portrait of his wife Lisa del Giocondo Mona Lisa (La Gioconda) (1503-1506), which to become the most famous picture in the world. Although the portrait was not finished in time and never delivered to the client. Leonardo received more important commission, he was to paint the Grand Council Chamber in the Palazzo Vecchio, the seat of government of Florence. The wall-painting, which Leonardo left unfinished in the spring of 1506 and which was destroyed in the middle of the XVI century depicted the Battle of Anghiari of 1440, when Florentine forces, together with their papal allies, defeated their Milanese opponents near the town of Anghiari. At the same time Michelangelo was commissioned to create a painting on the other wall of the same hall (the so-called Battle of Cascina), which was  never finished either.In 1506-1512 Leonardo lived mostly in Milan under the patronage of the French Governor of the town Charles d'Amboise. During these years he created The Leda and the Swan (c.1505-1510), which is known now only through a number of copies, second version of The Virgin of the Rocks (1506-1508), worked on the equestrian statue for General Giangiacomo Trivulzio, which was never realized, continued his anatomical studies. After the death of Charles d'Amboise in 1511, Leonardo accepted the protection of Giuliano de'Medici, brother of the future Pope Leo X, with whom he then traveled to the papal court in Rome. Leonardo, by now 61 years old, apparently hoped to become a court painter. But he never received any major commissions comparable to those already carried out by Raphael and Michelangelo from Leo X. He probably created at this time  St. John the Baptist (c.1513-1516), although there is one more John the Baptist (with the attributes of Bacchus) (c. 1513-1516), which is also attributed to Leonardo. In 1516 Leonardo received an invitation from French King Francis I to go to the French court, which he accepted. He was given residence in Cloux, not far from the King's residence in Amboise, and was appointed "the first painter, engineer and architect to the King". But his only obligation was to converse with the 22-year old King, who visited him almost daily. Leonardo died on the 2nd of May, 1519 in Cloux and was buried in the Church of St. Florentine in Amboise. Leonardo's reputation in his life-time was immense, and it was acknowledged visibly not only in the work of the foremost painters of the time in Florence - Fra Bartolommeo, Andrea del Sarto and, above all, Raphael - but also in Milan and northern Italy - by Correggio in Parma, and by Giorgione in Venice... abcgallery-Leonardo
Books: Leonardo : The Artist and the Man by Serge Bramly, Sian Reynolds (Translator). Paperback (March 1995), Leonardo Da Vinci by Diane Stanley. Library Binding (September 1996), Leonardo Lives : The Codex Leicester and Leonardo Da Vinci's Legacy of Art and Science by Tevor Fairbrother, et al. Paperback (January 1998)
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Art online: Leonardo 
Scritti on-line Leonardo da Vinci: Codice sul volo degli uccelli, Codice trivulziano, Il manoscritto H