How can we measure a skeleton’s motion in a furry animal as it moves through its environment? Researchers have developed a new 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 opens up a new ability to read out how animals interact with their environment and, as the brain and spinal cord drives movement, start unraveling the relationship between neuronal activity and complex behavior such as decision-making.