Over the last few decades small size plasma sources (i.e.~mm to ~ cm diameter) have been developed and applied to a variety of research fields ranging through materials processing and plasma medicine to electric propulsion.These discharges can be generated using a broad range of frequencies (direct current,radiofrequency,microwave) and gas pressure (from atmospheric pressure to orders of magnitude lower).Since plasma breakdown and steady-state depend on the pD factor (pressure x distance) high pressure operation yields small volume collisional discharges (i.e.jets,filaments,arcs...) while low pressure operation allows larger volumes of plasma to be generated.Power coupling,particle transport and steady-state properties greatly vary with external parameters and developing the science and technology aims at tuning the discharge properties for each application using a variety of techniques (spectroscopy,momentum diagnostics,computer fluid dynamics,particle in cell simulation techniques).