  We discuss here a model of QCD vacuum in terms of quark antiquark and gluon
condensates alongwith their fluctuations. The correlation functions of hadronic
currents in such a vacuum are evaluated to extract hadron properties. The
presence of fluctuations of the condensates are emphasized. The structure of
vacuum is then generalised to finite temperatures to study correlation
functions at finite temperatures. Finally, we discuss the vacuum structure at
finite densities with diquark condensates in a Nambu JonaLasinio type model.
The coupled mass gap and superconducting gap equations are solved
selfconsistently. For certain parameters of the model nontrivial solutions of
both the gap equations are obtained. The equation of state is also computed.
