Francisco de Goya became well known for the honest nature of his portraits, which made no effort to flatter the subjects. La Familia de Carlos IV is a brave portrait of the Spanish Royal family, completed in 1801.
Leonardo da Vinci's Mona Lisa is by far the best known painting in the world. It is also the most valuable, holding the Guinness World Record for the highest known insurance valuation in history.
Piet Mondrian’s Composition with Red, Yellow, Blue and Black (Composition En Rouge, Jaune, Bleu Et Noir)
Piet Mondrian pioneered geometric abstract painting. He used the term Neoplasticism to describe this style of work, which was inspired in part by cubist work coming from the Netherlands in the late 1900s.