  Using advanced sample engineering we performed simultaneous measurement of
intrinsic (interlayer) tunnelling characteristics and in-situ monitoring of
temperature in small Bi-2212 mesa structures. Together with a systematic study
of size-dependence of intrinsic tunnelling, this allowed an unambiguous
discrimination between artifacts of self-heating and gaps in electronic
spectrum of Bi-2212 High-$T_c$ superconductor. Finally, we analyze the
reliability of intrinsic tunnelling spectroscopy and discuss how it can be
improved.
