  Specially synthesized silica colloidal spheres with fluorescent cores were
used as model electrorheological fluids to experimentally explore structure
formation and evolution under conditions of no shear. Using Confocal Scanning
Laser Microscopy we measured the location of each colloid in three dimensions.
We observed an equilibrium body-centered tetragonal phase and several
non-equilibrium structures such as sheet-like labyrinths and isolated chains of
colloids. The formation of non-equilibrium structures was studied as a function
of the volume fraction, electric field strength and starting configuration of
the colloid. We compare our observations to previous experiments, simulations
and calculations.
