The egg without a shell

A chicken normally develops inside a calcium shell that quietly handles one job: it lets oxygen in and carbon dioxide out at exactly the right rate, in ordinary air. Colossal Biosciences says it has now built that shell from scratch. The embryos grow on a bioengineered silicone membrane inside a transparent 3D-printed lattice, tuned to match a real eggshell's gas exchange at normal atmospheric oxygen. Twenty-six chicks hatched and are living at the company's facility; the clear shell let the team watch each one develop.

"Essentially a modification of existing methods" — Katsuya Obara, who hatched chicks under plastic film in 2024

Growing a bird outside a real egg isn't new — researchers cultured quail in dishes in 1998, and another lab hatched chicks under plastic film in 2024. Those needed open containers and extra oxygen pumped in, and mostly failed. The claimed advance is the membrane that works in plain air, in a printed shell you could in principle scale up or injection-mold. The point of scaling is the part Colossal leads with: it wants to resurrect the moa, a 12-foot bird whose egg was roughly eighty times a chicken's — too big for any living surrogate to incubate. If you can't borrow a body, you build the egg.

The gap between the chicks and the moa is wide, and the people closest to the work are the least sure it's been crossed. There is no peer-reviewed paper — only a press release and a video — and no disclosed hatch rate, so 26 is a raw count, not a success ratio. Chickens remain the only bird whose embryos can currently be gene-edited at all, which is the actual bottleneck for editing anything extinct back into existence.