had not yet been discovered. The second decision was to occasionally ignore the order suggested by the atomic weights and switch adjacent elements, such as cobalt and nickel, to better classify them into chemical families. At the end of the 19th century, a number of discoveries were made in physics which paved the way for the development of modern physics – including Maria Skłodowska-Curie's work on radioactivity. In Europe by the 19th century, fashion had shifted away from such artistic styles as Mannerism, Baroque and Rococo and sought to revert to the earlier, simpler art of the Renaissance by creating Neoclassicism. Neoclassicism complemented the intellectual movement known as the Enlightenment, which was similarly idealistic. Ingres, Canova, and Jacques-Louis David are among the best-known neoclassicists. Just as Mannerism rejected Classicism, so did Romanticism reject the ideas of the Enlightenment and the aesthetic of the Neoclassicists. Romanticism emphasized emotion and nature, and idealized the Middle Ages. Important musicians were Franz Schubert, Pyotr Tchaikovsky, Richard Wagner, Fryderyk Chopin, and John Constable. Romantic art focused on the use of color and motion in order to portray emotion, but like classicism used Greek and Roman mythology and tradition as an important source of symbolism. Another important aspect of Romanticism was its emphasis on nature and portraying the power and beauty of the natural world. Romanticism was also a large literary movement, especially in poetry. Among the greatest Romantic artists were Eugène Delacroix, Francisco Goya, Karl Bryullov, J. M. W. Turner, John Constable, Caspar David Friedrich, Ivan Aivazovsky, Thomas Cole, and William Blake. Romantic poetry emerged as a significant genre, particularly during the Victorian Era with leading exponents including William Wordsworth, Samuel Taylor Coleridge, Robert Burns, Edgar Allan Poe and John Keats. Other Romantic writers included Sir Walter Scott, Lord Byron, Alexander Pushkin, Victor Hugo, and Goethe. Some of the best regarded poets of the era were women. Mary Wollstonecraft had written one of the first works of feminist philosophy, A Vindication of the Rights of Woman which called for equal education for women in 1792 and her daughter, Mary Shelley became an accomplished author best known for her 1818 novel Frankenstein, which examined some of the frightening potential of the rapid advances of science. In early 19th-century Europe, in response to industrialization, the movement of Realism emerged. Realism sought to accurately portray the conditions and hardships of the poor in the hopes of changing society.