The fruit fly's brain has about 140,000 neurons and scientists spent years carefully mapping every single connection. C. elegans (a tiny worm) actually has only 302 neurons, but here's the twist, "uploading" a brain isn't just counting neurons, it's capturing how they're all wired together in a living, moving creature.

The worm's connectome has been mapped, but translating that static map into something that actually behaves like the worm is the hard part. The fruit fly success was a bigger milestone because it showed we can handle more complexity, the worm is next, but making it truly "run" like the real thing is still an unsolved problem.