https://motherboard.vice.com/en_us/article/neg5vg/biologists-grew-a-human-retina-in-a-dish

Scientists at Johns Hopkins University replicated a human retina in a dish to explore how the eye’s color-detecting cells develop. Their findings could help premature babies better develop eyesight, and the elderly keep theirs for longer.

If you’re imagining a whole eyeball lolling around in a wet dish, it wasn’t quite that gory; without a microscope, it looked like a tiny translucent lump of goo.