A paralysed man was able to write after two revolutionary chips were implanted into his brain.
The unnamed 65-year-old cannot move from the neck down as a result of a spinal cord injury in 2007.
To help him communicate, scientists from Stanford University implanted so-called brain-computer interfaces (BCIs) into the left side of his vital organ, where hand movements are regulated.
These interfaces detected signals given out by the man's nerve cells when he imagined writing certain letters.
A computer then interpreted the pen-tip motion the man intended to make, with the letters appearing on a screen, with up to 99% accuracy.
His typing speed was even "comparable" to that of a smartphone user.
"Imagine if you could only move your eyes up and down but couldn't move anything else," lead author Dr Frank Willett told AFP.
"A device like this could enable you to type your thoughts at speeds that are comparable to that of normal handwriting or typing on a smartphone."
BCIs are known to help people who are unable to speak or move to communicate with others.
Research has largely focused on the interfaces' ability to help a patient reach, grasp or click the buttons of a computer mouse.
Their potential for "faster rates of communication" like writing or touch-typing was less clear, however.
The Stanford scientists therefore developed an "intracortical BCI that decodes attempted handwriting movements from neural activity" and "translates it to text in real time".
The unnamed man was fitted with two pill-sized implants on the left side of his brain to detect nerve cell firing in the motor cortex.
Sensors then transmitted these signals to a computer, where an artificial intelligence algorithm translated them into text.
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Results, published in the journal Nature, reveal the unnamed man typed at a speed of 90 characters per minute.
The letters that appeared on the screen were accurate 94.1% of the time, rising to 99% when an autocorrect function was added to the computer.
The man's typing speed was deemed to be "comparable to typical smartphone" users of the same age, who typically manage around 115 characters per minute.
He even managed to give some poignant advice to his younger self: "Be patient it will get better."
The scientists have stressed their research is a "proof of concept" study in just a single individual, adding their BCI is "not yet a complete, clinically viable system".
It is unclear if the device could enable a paralysed person to write in a more complex way, like capital letters, or edit what they have already typed.
With further research, however, such an implant could be available in "years as opposed to decades", according to Dr Willett.