SAN FRANCISCO — Microsoft is trying to home in on a younger, chattier demographic with two new cellphones centered on social networking.

The Kin One and Kin Two allow users to keep closely synched with sites like Facebook, Twitter and MySpace. The start menu displays a montage of photographs from friends with notes about what they are doing rather than a more traditional menu that caters to phone functions. The Kins also have touch screens, links to the Zune music service and high-powered cameras for capturing photographs and video.

“This is aimed at 15- to 30-year-olds who are social-networking enthusiasts,” said Robert J. Bach, president of Microsoft’s entertainment and devices division, who introduced the phones at a news conference here Monday.

Phone makers like Nokia and Samsung have long built a variety of models, including those aimed at younger buyers, many of which also link to social-networking sites. But in its focus on social networking, Microsoft has taken one of the more aggressive stances in going after this market, which the company believes is receptive to a fresh pitch.