We study the phase ordering colloids suspended in a thermotropic nematic li
quid crystal below the clearing point T-ni and the resulting aggregated str
ucture. Small (150 nm) PMMA particles are dispersed in a classical liquid c
rystal matrix, 5CB or MBBA. With the help of confocal microscopy we show th
at small colloid particles densely aggregate on thin interfaces surrounding
large volumes of clean nematic liquid, thus forming an open cellular struc
ture, with the characteristic size of 10-100 mum inversely proportional to
the colloid concentration. A simple theoretical model, based on the Landau
mean-field treatment, is developed to describe the continuous phase separat
ion and the mechanism of cellular structure formation.