Morning Musume Hello! Project Images

Morning Musume (モーニング娘。), sometimes referred to as Momusu (モー娘。), is one of the most successful Japanese pop idol girl groups, holding the second highest overall single sales (of a female group) on the Oricon charts as of February 2012, with the Oricon record of most top ten singles with an amount of 50, and they have sold over 18 million copies in Japan alone. They are the lead group of Hello! Project, which specialises in upbeat, pop-oriented music coupled with dance performance. The project is managed and produced by Tsunku, who composes vast majority of their song's lyrics and melodies. Over the years, the group produced several splinter groups, and often worked with other Hello! Project acts, including Country Musume, Berryz Kobo, Cute, Melon Kinenbi, and v-u-den.

Since their expansion into the Chinese-speaking market in 2007, the group officially adopted the name Jou An Sao Nu Jou (Zǎo Ān Shào Nǚ Zǔ, Traditional Chinese: 早安少女組, literally "good morning girl's group"). In recent years, the group have been making a concerted attempt to break into new markets in Asia, Europe and the US, performing at EXPOs worldwide.

The group's name can be translated as Morning Girls, as the name suggests, (with some degree of variation) it consists of members mostly in their late adolescence and early 20s. This has remained more or less unchanged since its formation in 1997 because the group maintains a "school-like" system for their continuous line-up changes, with older members "graduate" and new, usually younger, members selected from nationwide auditions admitted to the group annually.

source: en.wikipedia.org