Adaptive Keyboard
At one point in history, Apple was known to experiment with this with MacBook Pro 2016 release (Apple Reportedly Working On A Magic Keyboard With E-Ink Display Keys - Video](https://wccftech.com/apple-reportedly-working-magic-keyboard-eink-display-keys-video/)) They used e-ink for adaptive keyboards. Then they scraped it, and rumors indicated they moved to OLED, now seen on touch-bar macs. The rumor, however, did not end on the touch bar; the entire keyboard area was made with OLED buttons.