Micronesia is divided politically among several sovereign countries. One of these is the Federated States of Micronesia, which is often called "Micronesia" for short and is not to be confused with the overall region. The Micronesia region encompasses five sovereign, independent nations—the Federated States of Micronesia, Palau, Kiribati, Marshall Islands, and Nauru—as well as three U.S. territories in the northern part: Northern Mariana Islands, Guam, and Wake Island.
Micronesia began to be settled several millennia ago, although there are competing theories about the origin and arrival of the first settlers. The earliest known contact with Europeans occurred in 1521, when Ferdinand Magellan reached the Marianas. The coinage of the term "Micronesia" is usually attributed to Jules Dumont d'Urville's usage in 1832, however Domeny de Rienzi had used the term a year previously.
Micronesia is a region that includes approximately 2100 islands, with a total land area of 2,700 km2 (1,000 sq mi), the largest of which is Guam, which covers 582 km2 (225 sq mi). The total ocean area within the perimeter of the islands is 7,400,000 km2 (2,900,000 sq mi).
There are four main island groups in Micronesia: