Overview: Bell's invention, the telephone, was the first device capable of reproducing sound. But it couldn't record it. Thomas Edison's invention of the phonograph brought us the first device capable of capturing sound to be played back later. How did Edison figure this out? By combining one of his earlier ideas with the ideas in the telephone, Edison was able to bring a revolutionary product to market (well, sort of). This week, we're exploring how Edison thought up his device.