Sketchbooks are like visual diaries for artists.
Artists often use them for planning and developing their work. The most famous artist sketchbooks are those of Leonardo da Vinci. His sketchbooks are filled with drawings, diagrams and written notes of things he saw and ideas he came up with. Picasso produced 178 sketchbooks in his life time. He often used his sketchbooks to explore themes and make compositional studies until he found the right idea and subject for a larger painting on canvas.