  We present a novel approach to constrain the formation channels of
Ultra-Compact Dwarf Galaxies (UCDs). This inhomogeneous class of objects of
remnants of tidally stripped dwarf elliptical galaxies and high mass globular
clusters. We use three methods to unravel their nature: 1) we analysed their
surface brightness profiles, 2) we carried out a direct search for tidal
features around UCDs and 3) we compared the spatial distribution of GCs and
UCDs in the halo of their host galaxy.
  Based on FORS2 observations, we have studied the detailed structural
composition of a large sample of 97 UCDs in the halo of NGC1399, the central
galaxy of the Fornax cluster, by analysing theirsurface brightness profiles. We
derived the structural parameters of 13 extended UCDs modelling them with a
single Sersic function and decomposing them into composite King and Sersic
profiles. We find evidence for faint stellar envelopes at mu=~26 mag\arcsec^-2
surrounding the UCDs up to an extension of 90pc in radius.
  We also show new evidence for faint asymmetric structures and tidal tail-like
features surrounding several of these UCDs, a possible tracer of their origin
and assembly history within their host galaxy halos. In particular, we present
evidence for the first discovery of a significant tidal tail with an extension
of ~350pc around UCD-FORS2.
  We searched for local overdensities in the spatial distribution of globular
clusters within the halo of NGC1399, to see if they are related to the
positions of the UCDs. We found a local overabundance of globular clusters on a
scale of <1kpc around UCDs, when we compare it to the distribution of globulars
from the host galaxy. This effect is strongest for the metal-poor blue GCs. We
discuss how likely it is that these clustered globulars were originally
associated with the UCD.
