A Yale research team restored organ and cellular functions in dead pigs. Its findings may lead to a redefining of when something is considered “dead.”

In a recently published study in the science journal Nature, the Yale researchers assert the biochemical degradation that occurs after an animal’s heart stops beating doesn’t have to be as massive or permanent.

Building off of a previous study, the research team took some pigs and induced cardiac arrest in anesthetized pigs.

An hour after the pigs were dead, the team used something called the OrganEx System, which is like the heart-lung machines used during surgeries, and an experimental mixture of fluids that promote cellular health.

Researchers found the hearts of the dead pigs started to faintly beat again, blood circulation was restored, and some vital organs had revived cellular functions.

The team said its most surprising observation was of involuntary muscular movements in the head and neck areas of the dead animals. The movements, according to the research team, indicated the preservation of some motor functions.

The research team said it’s a long way from reviving entire organs–let alone whole organisms.

When put under a microscope, however, the research team said it was hard to tell the difference between a healthy organ and one treated with OrganEx after death.

The findings could be pivotal for human health and organ transplants in the future, or it’s the start of a real-life George Romero zombie movie.