  Collective cellular movement plays a crucial role in many processes
fundamental to health, including development, reproduction, infection, wound
healing, and cancer. The emergent dynamics that arise in these systems are
typically thought to depend on how cells interact with one another and the
mechanisms used to drive motility, both of which exhibit remarkable diversity
across different biological systems. Here, we report experimental evidence of a
universal feature in the patterns of flow that spontaneously emerges in groups
of collectively moving cells. Specifically, we demonstrate that the flows
generated by collectively moving dog kidney cells, human breast cancer cells,
and by two different strains of pathogenic bacteria, all exhibit conformal
invariance. Remarkably, not only do our results show that all of these very
different systems display robust conformal invariance, but we also discovered
that the precise form of the invariance in all four systems is described by the
Schramm-Loewner Evolution (SLE), and belongs to the percolation universality
class. A continuum model of active matter can recapitulate both the observed
conformal invariance and SLE form found in experiments. The presence of
universal conformal invariance reveals that the macroscopic features of living
biological matter exhibit universal translational, rotational, and scale
symmetries that are independent of the microscopic properties of its
constituents. Our results show that the patterns of flows generated by diverse
cellular systems are highly conserved and that biological systems can
unexpectedly be used to experimentally test predictions from the theories for
conformally invariant structures
