  Despite the technological importance of supercritical fluids, controversy
remains about the details of their microscopic dynamics. In this work, we study
four supercritical fluid systems -- water, Si, Te, and Lennard-Jones fluid --
\emph{via} classical molecular dynamics simulations. A universal two-component
behavior is observed in the intermolecular dynamics of these systems, and the
changing ratio between the two components leads to a crossover from liquidlike
to gaslike dynamics, most rapidly around the Widom line. We find evidence to
connect the liquidlike component dominating at lower temperatures with
intermolecular bonding, and the component prominent at higher temperatures with
free-particle, gaslike dynamics. The ratio between the components can be used
to describe important properties of the fluid, such as its self-diffusion
coefficient, in the transition region. Our results provide insight into the
fundamental mechanism controlling the dynamics of supercritical fluids, and
highlight the role of spatiotemporally inhomogenous dynamics even in
thermodynamic states where no large-scale fluctuations exist in the fluid.
