When Leonardo da Vinci died on May 2, 1519, he left behind over 7,000 pages of handwritten notebooks. These were not ordinary notes. Leonardo filled them with drawings of human bodies, flying machines, water flows, and plant structures. He sketched inventions that would not be built for centuries. What makes the notebooks so remarkable as writing is how Leonardo combined words and images on every page. A drawing of a bird's wing might sit next to notes about how muscles work. A sketch of a river appears beside thoughts about erosion. Leonardo did not separate art from science -- his notebooks treated them as one subject. The writing itself is unusual. Leonardo wrote in mirror script, meaning every word runs right to left. You need a mirror to read it naturally. Historians believe he wrote this way because he was left-handed and it prevented ink from smearing. The notebooks were never published during his lifetime. After his death, they were scattered across Europe. The ones that survive are kept in museums and libraries in cities like London, Paris, and Milan. Today, scientists, artists, and writers study them. They show what happens when a curious mind writes down everything it notices.