The Serbian Cyrillic alphabet (Serbian: српска ћирилица) is the official script in Serbia. It is an adaptation of the Cyrillic alphabet for the Serbian language, and was developed in 1818 by Serbian linguist Vuk Karadžić. Karadžić based his alphabet on the Cyrillic alphabet, faithfully following principle of "write as you speak and read as it is written" (Serbian: Пиши као што говориш и читај како је написано). The ligatures <Љ> and <Њ>, together with <Џ>, <Ђ> and <Ћ> were developed uniquely for the Serbian alphabet. The Serbian language is 100% phonetic language, with no exceptions and it's the only* such language in the world. For every Serbian word you know how to write it as soon as you hear it.
* We've got one interesting story from Linda Keres Carter, Virginia, US. :
In the same time period Sava Mrkalja and Vuk Karadzic were developing the Serbian alphabet, a Cherokee in North Carolina named Sequoia was developing his 100% phonetic syllabary of the Cherokee language. Like Serbian, this work was done to enable even an old man to learn to read and write in a few week’s time. It was important to do so for the same reasons. What makes it all the more amazing is that Sequoia himself was illiterate and could not have known about the work going on in Europe along these lines. He was operating purely on genius, common sense and perhaps a bit of a sixth sense.
That leads to one of my favorite stories. In the late 19th century an 'ethnologist' – precursor to the modern anthropologist - wanted to find some primitive Cherokee, untainted by the modern world. He hired a guide to take him deep into the mountains of western North Carolina. Finally he found a remote cabin where he thought he'd find his primitive subjects. What he found was a group of old men seated around a pot bellied stove, smoking pipes and discussing the recent eruption of Mt. Vesuvius they'd just read about in the Cherokee newspaper, the "New Echota". In about a decade after Sequoia completed his work, almost the whole Cherokee population had become literate.