  The Super Proton Synchrotron (SPS) covers one of the most interesting regions
of the QCD phase diagram $(T - \mu_B)$. On the one hand there are indications
that the energy threshold for deconfinement is reached already at low SPS
energies. On the other hand theoretical calculations locate the QCD critical
end-point at energies accessible at the SPS. In this paper the NA49 signatures
of the onset of deconfinement are presented. Results are shown on pion
production, the kaon to pion ratio, slopes of transverse mass spectra
("temperature"), and event-by-event particle ratio fluctuations versus
collision energy, for central $Pb+Pb$ interactions. Next we show possible
indications of the critical point in event-by-event mean transverse momentum
and multiplicity fluctuations. Finally we discuss the future ion program of the
NA61/SHINE experiment (energy scan with light ions).
