For an easy, germ-free and eco-friendly shipping method, Tatami Kids uses vacuum compression for better transportation of mats. After three to five days, the creases and shrinking due to compression will naturally recover. To accelerate this expansion or if the mat has not expanded out fully after 5 days, please do the following:Steam the whole mat with a steaming iron or steamer for clothes (recommended)Iron any deep creases - like you would when ironing clothes.