  The configuration and evolution of coexisting mesoscopic domains with
contrasting material properties are critical in creating novel functionality
through emergent physical properties. However, current approaches that map the
domain structure involve either spatially resolved but protracted scanning
probe experiments without real time information on the domain evolution, or
time resolved spectroscopic experiments lacking domain-scale spatial
resolution. We demonstrate an elegant experimental technique that bridges these
local and global methods, giving access to mesoscale information on domain
formation and evolution at time scales orders of magnitude faster than current
spatially resolved approaches. Our straightforward analysis of laser speckle
patterns across the first order phase transition of VO$_2$ can be generalized
to other systems with large scale phase separation and has potential as a
powerful method with both spatial and temporal resolution to study phase
separation in complex materials.
