Natural rivers are not straight, and they are rarely idle. Instead, they bend and curve and sometimes appear to wriggle across the Earth's surface over time. That rivers can meander is obvious but how and why they do so is less well known. These questions are complicated by the fact that researchers have for the most part been unable to realistically create a meandering river in a laboratory. Scientists have previously created simulated streams that bend and branch, but they were not able to limit the river to only a single main flow path or maintain such dynamic motion past the initial bend formation. Working with a 6-by 11-meter river simulator, the Eurotank, van Dijk et al. created a dynamically meandering river. In so doing, the authors identified two conditions necessary to induce meandering: the availability of mixed sediment and a continuously varying upstream water source.