  Azimuthal anisotropy has been ubiquitously observed in high-energy
proton-proton, proton-nucleus, and nucleus-nucleus (heavy-ion) collisions,
shaking the early belief that those anisotropies must stem from utterly strong
interactions. This work reports a study of anisotropic expansion of cold
$^{6}$Li Fermi gases, initially trapped in an anisotropic potential, as a
function of the interaction strength that can be readily tuned by an external
magnetic field. It is found that the expansion anisotropy builds up quickly at
small interaction strength, without the need of utterly strong interactions. A
universal behavior of the expansion anisotropy is quantitatively observed
between cold-atom and heavy-ion systems, despite their vast differences in
physics. This universality will potentially unify a variety of disciplines in
nature, from the weakly interacting dilute systems of gases to the strongly
interacting quark-gluon plasma of the early universe.
