It would seem that written language, which was predated by spoken language by a very large margin, arose during the agrarian phase of human development, i.e., following the strictly hunter-gatherer phase, and for this reason, written language arose in different cultures at different chronological periods, as witnessed by the fact that the Neolithic Age, or New Stone Age, occured in different geographical regions at different chronological periods.*(1, 2) (If, according to the prevailing current thinking, the Out of Africa hypothesis has merit, then humans spoke a highly complex language before they began to migrate out of Africa to the four corners of the earth.)
The words of the Chinese language are composed of characters, which might roughly be compared to syllables in Western languages. In very ancient times, each word consisted of a single character, but over time, Chinese words came to consist of two to three characters, and eventually even more. Most Chinese words in currency today consist of at least two syllable-characters, such as, for example, Beijing, or bei jing, 北京, meaning the "northern capital", but may consist of, in principle, an unlimited number of characters, though practicality naturally limits this. One of the longer, modern Chinese words (note that in Chinese, the creation of new words is a pretty straightforward affair, given that one can simply combine existing concepts – represented by their respective characters – to create a new term) is the compound word, schizophrenia: 精神分裂症, which translates roughly to "split mind disease" and consists of at least seven characters (and some of them look as if they may well be compound characters).
The best way to think of the Chinese language is that it is made up of building blocks (characters) that offer seemingly infinite potential combinations, since the various building blocks can be combined in any number of ways. For this reason, the Chinese language is considered an open-ended language, meaning that there is no limit to how many words can be formed simply by combining two or more characters to form a new concept represented by a new word.
The largest Chinese dictionaries consist of about 56,000 individual characters, while everyday speech, including everyday written language, requires the knowledge of only about 3000 characters, and, in fact, even literary and scientific Chinese language only requires familiarity with about 6000 characters.