  Imaging of flux vortices in high quality MgB$_2$ single crystals has been
successfully performed in a commercial Field Emission Gun-based Transmission
Electron Microscope. In Cryo-Lorentz Microscopy, the sample quality and the
vortex lattice can be monitored simultaneously, allowing one to relate
microscopically the surface quality and the vortex dynamics. Such a vortex
motion ultimately determines the flow resistivity, $\rho_{f}$, the knowledge of
which is indispensable for practical applications such as superconducting
magnets or wires for Magnetic Resonance Imaging. The observed patterns have
been analyzed and compared with other studies by Cryo-Lorentz Microscopy or
Bitter decoration. We find that the vortex lattice arrangement depends strongly
on the surface quality obtained during the specimen preparation, and tends to
form an hexagonal Abrikosov lattice at a relatively low magnetic field. Stripes
or gossamer-like patterns, recently suggested as potential signatures of an
unconventional behavior of MgB$_2$, were not observed.
