This article reports on new studies that shed light on whether getting students into the lab earlier makes a difference. The belief that undergraduate research attracts students to careers in science--and makes them better candidates for such work--has gained almost universal acceptance in academe. But until recently, few researchers have studied whether or not that is actually the case. In the past few years, a small cadre of social scientists have, with grants from some of the largest supporters of undergraduate science research, begun systematically studying the effects on students. Three large studies verified some widely held notions about undergraduate research, but challenged other assumptions. It was found that undergraduates learn and grow significantly from their research experiences, but require a strong mentor relationship to do so. Such a time commitment may cost faculty members more than they gain from the additional lab help, one of the studies suggests. The end result may only slightly increase the number of students going on to earn Ph.D.'s.