Since there aren’t nearly enough human hearts available for transplant for patients that need them, scientists have been searching for ways to create an artificial heart that is viable for transplant. This week, science took a big step toward making this a reality after Chicago-based biotech company BIOLIFE4D announced it has successfully 3D-bioprinted a mini human heart.

The tiny heart was printed with patient-derived cardiac muscle cells and bioink made from extracellular matrix compounds that replicate the properties of the mammalian heart.  Earlier this year, the company bioprinted individual heart components, including valves, ventricles, and blood vessels. This, however, was the first time all these components were successfully printed together.

In the near future, the company hopes to bioprint a full-sized functioning human heart.