Despite the close association between a sweet aromatic scent and vanilla, fresh beans from the vanilla plant have no natural fragrance. For the characteristic aroma to develop, the beans must undergo a curing process that involves repeated daily exposure to the rays of the sun and nighttime sweating. During curing, the pods of vanilla beans develop numerous small crystals of vanillin, which are secreted by internal papillae and are the source of the scent commonly called vanilla. The amount of vanillin present in bean pods is often utilized to help determine their quality or grade, most cured pods secreting about two percent of their weight as the fragrant compound.