Living skeletal muscle that not only functions like the real thing but can heal itself has been engineered by scientists.
The lab-grown tissue, produced from immature pre-cursor cells, was demonstrated in mice.
Scientists believe it marks a significant step towards growing viable replacement muscle in humans.
Unlike previous examples of bioengineered muscle, the artificially-constructed muscle fibres contracted as strongly as their natural counterparts.
Satellite cells - dormant step cells that can be activated by injury to regenerate damaged tissue - were at the heart of the self-repair mechanism.
The secret was supplying them with the right environment, the researchers writing in the journal Proceedings of the National Academy of Sciences said.
"Simply implanting satellite cells or less-developed muscle doesn't work as well," said Mark Juhas, a member of the team from Duke University in Durham, US.
"The well-developed muscle we made provides niches for satellite cells to live in, and, when needed, to restore the robust musculature and its function."
Stimulating the tissue with electric pulses to make it contract showed that the engineered muscle was more than 10 times stronger than any of its predecessors.
After suffering damage from snake venom toxin, the satellite cells stepped in, activating, multiplying and repairing the injured muscle fibres.
The scientists watched the muscle integrate and mature in a living animal through small glass windows inserted into the backs of mice.
A genetic modification causing the muscle fibres to produce fluorescent flashes when they contracted made it possible to observe them growing stronger in real time. The stronger they got, the brighter they flashed.
"We could see and measure in real time how blood vessels grew into the implanted muscle fibres, maturing toward equalling the strength of its native counterpart," said Mr Juhas.
The scientists now plan to investigate the muscle's potential for repairing real injuries and treating disease.