To make a pound of saffron, over two hundred thousand stigmas from crocus sativus flowers must be harvested by hand. That's why saffron is the world's most expensive spice, and also why so there are so many fakes on the market. Fortunately, a little of the good stuff goes a long way--it only takes a few threads to add saffron's distinct yellow color and earthy aroma to a family meal of paella or bouillabaisse. You can buy saffron either as as unprocessed stigmas (called saffron threads) or powdered. The threads should be red with orange tips. Threads lacking orange tips may be dyed, so avoid them. The quality of powdered saffron is measured by its Minimum Coloring Strength. The higher the Minimum Coloring Strength, the less saffron you need to use. A typical level is 180, and a level of 220 or higher is quite good. Some cooks prefer the threads to the powder, since it's hard to detect if the powder has been adulterated. Powdered saffron, though, is easier to use, since it can be added directly to a dish, while the threads need to be steeped in hot water first.