We present the results of a field experiment conducted within the Harvard Medical School system of hospitals and research centers to understand how colocation impacts the likelihood of scientific collaboration. We introduce exogenous colocation and face-to-face interactions for a random subset of biomedical researchers responding to an opportunity to apply for a research grant. While the overall baseline likelihood of any two researchers collaborating is small, we find that random colocation significantly increases the likelihood of pair-level co-application by almost 70%. The effect of exogenous colocation on subsequent collaboration was greater for previous coauthors, pairs including a woman, and pairs researching similar clinical areas. Our results suggest that matching between scientists may be subject to considerable frictions-even among those in relatively close geographic proximity and in the same organizational system. At the same time, even a brief and focused intervention facilitating face-to-face interactions can provide information that impacts the formation of scientific collaborations.