Spheroids are three dimensional cell models that can mimic some organs, tumors, and other biological systems for drug testing. Like organoids and organs-on-a-chip, spheroids are breaking in to drug development as a promising alternative to animal models. I am joined by Madhu Lal Nag, MBS PhD from the 3D in vitro model company InSphero, to discuss the development and future potential of these tiny cellular machines.