Gravitational phenomena are yet again at the center stage of both experiment and theory. On the theoretical side, there are renewed efforts to efficiently calculate gravitational processes as well as in detail understand gravity as a quantum theory. Recent progress has come from the double copy, which relates scattering amplitudes in gravity with those of non-abelian gauge theories. This talk will give a gentle introductory review to the topic of the double copy, as well as the underlying (square)-root mechanism that enables the double copy to work: the color-kinematics duality in gauge theory. The talk will also briefly summarize the status of current results that both broadens the scope of the double copy and probes deeper into the mathematical details of the color-kinematics duality.