A team of researchers from several institutions in Germany and Israel has used theoretical analysis to explain the conditions under which mega-ripples form in areas where sand dunes rise. In their paper published in the journal Nature Physics, the group describes combining field measurements with theory to come up with an explanation for mega-ripples. N. M. Vriend and P. A. Jarvis with the University of Cambridge offer a News & Views piece on the work done by the team in the same journal issue.