Doctors have now brought an adult heart back to life to transplant it into a person in need of a new organ for the first time in the US.
Duke University surgeons harvested the heart from a dead donor whose blood had already stopped circulating through their body.
They then used a pioneering technique to run blood back into the disembodied heart, so it would beat once more, a process documented in a surreal video tweeted by one of the doctors involved in the historic operation.
The heart was successfully transplanted into a recipient, a win that suggests far more will be eligible for donation in the future as doctors are able to beat the clock and keep the organ alive for outside of a body.
A human heart was transplanted for the first time ever in 1967 in South Africa. A year later, Stanford University doctors performed the first such transplant in the US.
By 2018, over 3,400 heart transplants were performed across the US.
Heart transplants are now relatively common, but there's a constant shortage of organs - hearts as well as others, like livers, lungs and kidneys - in the US and worldwide.
Less than half of Americans in the US - about 45 percent - are registered as organ donors.
The pool shrinks further after they pass away.
Many organs are too damaged or in poor conditions that render them unusable.
Still others may be cast aside based on their donors' medical histories, lifestyles or infections they've contracted.
The transplant wait list in the US is over 100,000 people long, and 20 die every day waiting for new organs.
In an effort to address this, doctors are constantly working on new ways to broaden the donor pool.
Simply asking more Americans to register as organ donors isn't enough. In recent years, the transplant community has expanded that pool most significantly by allowing the transplantation of organs from donors who tested positive for hepatitis C.
In addition to meeting health