Though an estimated 60 million people around the world have atrial fibrillation, or A-fib, a type of irregular and often fast heartbeat, it’s been at least 30 years since any new treatments have been developed. This is because researchers haven’t had accurate models of the human heart to study. Thanks to new developments from Michigan State University scientists, that is no longer the case.

In 2020, MSU researcher Aitor Aguirre and his team started creating and perfecting tiny working models of the human heart known as organoids. Now, these organoids can be modified to replicate atrial fibrillation, or A-fib.

Roughly the size of a lentil, the three-dimensional heart organoids are so accurate that researchers can study heart development, diseases and drug responses in ways that were previously impossible. The organoids’ rhythmic beating is so strong that it can be seen without a microscope.