Indigo Dyeing
Indigo is a natural process of dyeing textiles that has been dated to 6,000 years ago. The oldest known fabric dyed with this plant was found in Peru. Indigo is extracted from a plant and goes through a fermentation process to produce its vivid blue color. Historically, indigo is used in dyeing wool, silk, and cotton. Most indigo dye used today is a synthetic dye, and not the traditional dye made from plant materials.
Indigo plant
Photographer unknown licensed under CCBY-SA