Tatami mats are traditional Japanese floor coverings made from woven rush grass (igusa) wrapped around a rice straw core. Originally used by nobility during the Heian period, they became standard flooring in Japanese homes and are measured in standardized sizes called jō. Tatami mats have a pleasant, natural fragrance and provide excellent insulation properties that help regulate room temperature and humidity. These mats are characterized by their distinctive green or yellow-beige color and bordered edges, typically sewn with decorative fabric. In traditional Japanese architecture, rooms are often designed around tatami arrangements, with specific rules for their placement and the number of mats determining the room size.