In reality research centres using animals must follow strict and detailed EU laws to ensure the most appropriate environment for laboratory animals and that their needs are met. For example mice and rats are housed in cages that contain shredded paper and pieces of wood to build nests and to find refuge. Animals also have opportunities to climb and explore. They are encouraged to perform their habitual activities, which reduce stress. Scientists have no reason to mistreat research animals and good reason for treating them well, because the use of unhealthy, stressed or frightened animals reduces the reliability of an experiment’s results. Staff are trained to handle the animals in a way that will reduce any potential stress.