How can we measure a skeleton’s motion in a furry animal as it moves through its environment? Researchers at the Max Planck Institute for Neurobiology of Behavior have developed a method to quantify skeletal motion in freely moving rodents in a new level of accuracy and detail. It is based around building a skeleton-model that calculates bone joint movement using basic anatomical principles, such as joint rotation limits, and speeds at which bodies can move. This approach, published in Nature Methods, opens up a new ability to read out how animals interact with their environment and start unravelling the relationship between neuronal activity and complex behavior such as decision-making.