Piano sonatas (Beethoven)
Ludwig van Beethoven wrote his 32 piano sonatas between 1795 and 1822. Although originally not intended to be a meaningful whole, as a set they compose one of the most important collections of works in the history of music. Hans von Bülow called them "The New Testament" of the piano literature (Johann Sebastian Bach's "The Well-Tempered Clavier" being "The Old Testament").
Ludwig van Beethoven
He also explored new directions and gradually expanded the scope and ambition of his work. Some important pieces from the early period are the first and second symphonies, the set of six string quartets Opus 18, the first two piano concertos, and the first dozen or so piano sonatas, including the famous "Pathétique" sonata, Op. 13.