The brain is the center of our reality, but it's nothing without the heart. A new discovery by English researchers opens the door to greater understanding of how the heart forms.

This scan was taken on Day 8 in mice — which would be equivalent to 21 days in humans.

At this point, cells are activating certain genes that dictate what part of the heart it will eventually become.

The red arch of cells here is called the cardiac crescent. It will form the heart's four chambers.

If we can learn how heart cells form, we can recreate them in a lab for people who need them, like heart attack survivors.

The cells in green will become cardiomyocytes, or the muscle of the heart.

Those cells in green are already showing slow, rhythmic contractions.

Twelve hours later, the heart starts to look very different...

This is the linear heart tube stage. It has been slowly contracting for several hours, at this point.

Each color here represents a different cell type that will eventually contribute to a whole, functioning heart.