  Colloidal particles dispersed in a partially ordered medium, such as a liquid
crystal (LC) phase, disturb its alignment and are subject to elastic forces.
These forces are long-ranged, anisotropic and tunable through temperature or
external fields, making them a valuable asset to control colloidal assembly.
The latter is very sensitive to the particle geometry since it alters the
interactions between the colloids. We here present a detailed numerical
analysis of the energetics of elongated objects, namely prolate ellipsoids,
immersed in a nematic host. The results, complemented with qualitative
experiments, reveal novel LC configurations with peculiar topological
properties around the ellipsoids, depending on their aspect ratio and the
boundary conditions imposed on the nematic order parameter. The latter also
determine the preferred orientation of ellipsoids in the nematic field, because
of elastic torques, as well as the morphology of particles aggregates.
