Chillis are members of the capiscum family of all shapes, sizes and colours which grow in tropical and sub-tropical countries. They are green or red, often tapered and contain twice as much capsaicin as red peppers, which is why they provide so much heat to food. They are often available in dried or powdered forms. Colour is not necessarily a guide to the heat, which is measured in Scoville units (named after Wilbur Scoville). Generally speaking the scale goes from small and pointed, with thin skins, having the most heat through to large and blunt having the least. The greatest heat is contained in the membranes and seeds, which are attached to the "placenta" of the chilli. Certain chillis are almost only available dried while others are traditionally used in their fresh form. Aromatic chillis are often eaten raw in salads and salsas in Latin America.