  We present recent advances in the instrumentation and analysis methods for
quantitative imaging of concentrated colloidal suspensions under flow. After a
brief review of colloidal imaging, we describe various flow geometries for two
and and three-dimensional (3D) imaging, including a `confocal rheoscope'. This
latter combination of a confocal microscope and a rheometer permits
simultaneous characterization of rheological response and 3D microstructural
imaging. The main part of the paper discusses in detail how to identify and
track particles from confocal images taken during flow. After analyzing the
performance of the most commonly used colloid tracking algorithm by Crocker and
Grier extended to flowing systems, we propose two new algorithms for reliable
particle tracking in non-uniform flows to the level of accuracy already
available for quiescent systems. We illustrate the methods by applying it to
data collected from colloidal flows in three different geometries (channel
flow, parallel plate shear and cone-plate rheometry).
