An extraordinarily important but seemingly mundane computer problem is how to represent different written languages.

Nevermind, just translating words or letters between languages: how about things like the Thai "End of Story" punctuation character, different dialects and inflections in languages, how about making it extensible to new
languages, etc.

Unicode is the system built up to organize the messiness of human written communication and it’s a stunning design acheivement how the characters are allocated across the different "planes" of the specification.

Linden Labs (makers of SecondLife) have a Unicode in 5 Minutes wiki page that both succinctly covers the topic and has some really top notch illustrations of the concepts involved.