Chilli powder is a spice blend based on dried, ground chillies, often mellowed and extended with ground sweet peppers, oregano, cumin, and garlic. Pure ground chilli is hotter and simpler; the blended powder is the Tex-Mex seasoning for chilli con carne, tacos, and rubs. Heat comes from capsaicin, measured in Scoville units, and varies hugely between products. It should be added judiciously and bloomed in oil to release flavour. Like all ground spices it loses potency with age and should be stored airtight away from light. It is a defining flavour of Mexican-influenced cooking worldwide.