From Russia to America
Zworykin studied in St Petersburg under Professor Boris Rosing, who was experimenting with transmitting images electronically. After the revolution he left for the USA, and in 1923, at Westinghouse, filed a patent for a fully electronic television system.
The iconoscope
At RCA he developed the iconoscope camera tube, unveiled in 1933. The image from the lens fell onto a mosaic of tiny light-sensitive dots, and an electron beam read it line by line. The same principle, breaking an image into dots and lines, is used by today's cameras too, except they have a chip instead of a vacuum tube.
The battle for television
He disputed priority with the young inventor Philo Farnsworth, who had already transmitted an electronic image back in 1927. RCA ended up having to pay him licensing fees. Television therefore doesn't have a single father, but Zworykin is among the most important. At RCA he later also contributed to the development of the electron microscope.