In textbooks, rain is often considered either the first or final step in the Earth's global water cycle, either way marking a role of special significance. Its presence brings a nurturing flow of fresh water or a devastating flood. Its absence can parch the land. But while rain is spawned from large clouds, its measurement and detection hinge on the small-scale wobbles and interactions described by rainfall microphysics. In the AGU monograph Rainfall: State of the Science, editors Firat Y. Testik and Mekonnen Gebremichael explore the diverse body of research on all aspects of rainfall science. In this interview, Eos talks to Firat Testik.