In his classic etymological dictionary Shuowen Jiezi written nearly 2000 years ago, Xu Shen showed how every character can be analyzed by breaking it into component characters, which themselves can be broken down further, so that ultimately only a couple hundred root pictographs and ideographs (wen) generate all of the characters. Zhongwen.com and its associated printed dictionary show this generation process graphically for over 4000 characters using a series of zipu or "character charts/genealogies" that each start with one of the wen from Shuowen Jiezi. Without any system for cross-referencing, Xu Shen had to break his dictionary into manageable sections, starting each one with a bushou or "section heading" (conventionally mistranslated as "radical") that was a component for other characters in that section but not always a root wen. This bushou system has been the organizing principle for almost all subsequent Chinese dictionaries, but it arbitrarily focuses on only a single component of each character. In contrast the zipu system allows any character to be found if the viewer knows any part of the character or knows any character which shares the same component. The zipu follow traditional Chinese etymologies based mainly on the "small seal" characters that were standardized about 2,200 years ago in the Qin Dynasty. Modern researchers have obtained a better understanding of the earlier evolution of characters before they were standardized, but the traditional etymologies are more useful for students and remain the standard reference point for all subsequent research. Moroever, their widespread study over the centuries has meant that the traditional etymologies themselves have affected the usage, survival, and evolution of Chinese characters.