The hard sciences and engineering have benefitted immensely from interdisciplinary collaboration.  But what can interdisciplinary teamwork offer the behavioral sciences? In this talk, I will introduce a new tool called a “megastudy,” defined as a massive field experiment in which the effects of many different policy interventions designed by different teams of scientists are compared in the same population on the same objectively measured outcome for the same duration.  I will share results from four megastudies that my team has conducted over the last several years involving millions of Americans to illustrate the potential as well as the limits of these many-armed randomized controlled trials.