Woad is a plant, specifically known as Isatis tinctoria, that has been used for centuries to produce a blue dye. This dye is derived from the leaves of the plant and was historically significant in Europe, particularly during the Middle Ages. Woad was a popular alternative to indigo, another blue dye source, and was used to color textiles and clothing. In addition to its dyeing properties, woad has also been used in traditional medicine. The leaves contain compounds that have been studied for their potential health benefits, including anti-inflammatory and antimicrobial properties. Today, woad is less commonly used, but it remains of interest to those studying natural dyes and herbal remedies.