This document traces the evolution of headphones from the early 20th century to modern times. It outlines some key developments such as the introduction of headphones by Brandes in 1919, the popularization of headphones by Beyerdynamic in the 1930s, the invention of portable headphones with the Sony Walkman in 1979, and the rise of Bluetooth technology in 2000. The summary also notes that early headphones were bulky and uncomfortable, whereas modern headphones are smaller, more affordable, and safer to use.