Malcolm Little, later known as Malcolm X, spent his early adult years involved in criminal activity in Boston and New York and was convicted of burglary in 1946, receiving a sentence of several years in prison while still in his early twenties, with little formal education and, by his own later account, barely functional handwriting.
In prison, he became increasingly frustrated by how limited his own vocabulary was, unable to properly express the ideas he was beginning to encounter through reading. He decided to copy an entire dictionary by hand, page by page, in his own handwriting, as a way of forcing himself to actually absorb and retain every word's meaning and spelling.
This self-directed education continued well beyond the dictionary — he read voraciously in the prison library on history, religion, and philosophy, using nearly all his available time to build an intellectual foundation he had not had access to before, while also converting to the Nation of Islam during his imprisonment.
After his release, he became one of the most prominent and articulate voices of the civil rights era, known for his sharp, disciplined rhetorical style — a directly traceable outcome of the years he had spent in a prison cell teaching himself, word by word, how to think and argue with precision.