  Studying transient phenomena with the Very Long Baseline Interferometry
(VLBI) technique faces severe difficulties because the turnaround time of the
experiments from the observations to the scientific result is rather long. The
e-VLBI technique has made it possible to transfer the data from a number of
European VLBI Network (EVN) telescopes to the central data processor at JIVE
through optical fibres, and correlate them in real time. The main goal of this
paper is to introduce this rapidly developing new technique, by presenting
observational results from a recent experiment. We observed SN2001em, a Type
Ib/c supernova with an e-VLBI array and the Multi-Element Radio Linked
Interferometer Network (MERLIN) in the UK. The source is marginally detected in
our observations. We cannot make definite conclusions whether it is resolved at
1.6 GHz or not. Our data show that SN2001em either started fading in the last
couple of months, or its radio spectrum is inverted at low
frequencies,indicating free-free or synchrotron self-absorption. This is quite
unusual, but not unprecedented in radio SNe.
