A US science-mentoring service is seeking more advisers after a surge in demand. Since launching an enrolment campaign on Facebook, LinkedIn and Twitter in September, MentorNet, a non-profit group in Santa Clara, California, has signed up 320 graduate and undergraduate students, largely women and mainly from minorities, who want mentors in research and industry. Since 1997, MentorNet has made 30,000 connections, using grants and fees from about 100 US universities. The economy and tight university budgets have hindered expansion, but social media have helped to extend the service beyond member universities, says president and chief executive David Porush.