Traditional electromagnetic pickups are either single-coil or double-coil. Single-coil pickups are susceptible to noise induced by stray electromagnetic fields, usually mains-frequency (60 or 50 hertz) hum. The introduction of the double-coil humbucker in the mid-1950s solved this problem through the use of two coils, one of which is wired in opposite polarity to cancel or "buck" stray fields.
Guitars have been played since the Renaissance era, after descending from the ancient Greek instrument, the kithara. Or, at least, that's how the theory goes: the only real proof for this is the similarities between the Greek word and the Spanish word, quitarra. Early guitars often had four strings, evolving into the six-string version we know today in the late 1600s. Anton Stradivari, the famous violin-maker, also had a hand in making guitars. There's now only one Stradivarius guitar left in existence.