Indigo dye is a natural dye derived from the leaves of the Indigofera plant. It has been used for thousands of years to color fabrics, particularly cotton, and is known for its deep blue hue. The dyeing process involves fermenting the leaves to extract the indigo pigment, which can then be applied to textiles. Historically, indigo dye was highly valued and often referred to as "blue gold." It played a significant role in various cultures, including in India, where it was a major export, and in West Africa, where it was used in traditional textiles. Today, indigo is still popular in fashion and textile industries.