Tokyo Metro started out as a private company called Tokyo Chikatetsudo (Tokyo Subway) which built the Ginza Line (Asakusa - Ueno portion) in 1927. This was the first subway to be built in the entire Orient.
In 1941, Tokyo Chikatetsudo was combined with other subway lines to form the Teito Rapid Transit Authority (TRTA), which was owned by the Ministry of Railroads (Later the Ministry of Land, Infrastructure, Transport and Tourism.) The Teito in its name means "Imperial Capital", referring to Tokyo.
TRTA logo used from 1960s to 2004
Starting with the Marunouchi Line in 1954, the TRTA went on a building spree, connecting just about every area of Tokyo by subway. The Ginza and Marunouchi Lines are both powered by a third-rail but all train lines built after were switched to overhead wires. With this switch, the TRTA was able to connect their train lines with other train lines including the Japanese National Railways (Later became JR), Odakyu and Tokyu.
In 2004, the TRTA transferred all of its assets to Tokyo Metro which currently operates all of their lines. Tokyo Metro is currently naming their newer trains in the 10000s to distinguish them from the TRTA trains in the 1000s and the later 0X Series trains.
Yurakucho, Tozai, 03 Series, 05 Series, 06 Series, 07 Series, 15000 Series and 16000 Series photos courtesy of Railstation.net 01 Series photo Couretesy of The RW Place