Louis Braille lost his sight at the age of three after accidentally injuring one eye with a tool in his father's leatherworking shop, an injury that became infected and eventually spread to his other eye as well, leaving him completely blind by around age five, in a period when blind children had very few educational options available to them at all.
At ten, he was admitted to one of the first schools for blind children in the world, in Paris, where students were taught to read using a system of large, raised, embossed letters that were slow to read and expensive to produce in books, sharply limiting how much reading material was actually accessible to blind students.
In 1821, a former soldier visited the school and demonstrated a nighttime military communication code that used raised dots rather than letters, allowing soldiers to read silent messages in the dark. Braille, then twelve, recognized the potential immediately and spent the next several years adapting and refining the concept into a full, practical reading and writing system based on combinations of six raised dots.
He completed the core of what became known as Braille by the time he was fifteen, and continued refining it as a teacher at the same school he had once attended as a student. The system was not widely adopted during his own lifetime, facing resistance even from some blind educators skeptical of a system devised by a very young student, but it was formally adopted after his death and remains, with only minor changes, the standard reading system for blind people worldwide today.