The Piccolo is a small flute (the Italian word piccolo means small). It is exactly half the size of a standard flute, and is pitched one octave higher. It is the highest pitched instrument of the woodwind family. Music for the piccolo is written one octave lower than it sounds, so as to minimize the need for ledger lines..
It evolved at the beginning of the 19th century. Beethoven uses it in Symphony no 5, and also in his 6th Symphony - the Pastoral. Tchaikovsky makes extensive use of the piccolo.