Piet Mondrian was a Dutch painter born in 1872 who is known for developing an abstract style using primary colors, black lines, and rectangles. He began his career painting realistic landscapes but was influenced by artistic movements like Fauvism and Cubism. His mature style featured geometric shapes, thick and thin black lines separating rectangles and squares filled with red, yellow, and blue. The document provides instructions for students to create their own artwork in Mondrian's style using an online photo editor.