This thesis is a cumulative dissertation that consists of four papers addressing the different aspects of complex plasmas. The first paper addresses the issue of structural properties of complex plasma in elongated dc discharge chamber where 3D reconstruction of particles positions revealed the locally enhanced structural properties that indicate that the system was near crystallization. The second paper enclosed in this thesis is focused on fundamental gas thermodynamic properties. The convective motion of particles in complex plasma experiments is a common effect. By detailed analysis it was found that the convection of the gas is produced by the thermal gas creep effect. The main result of this work lies in the confirmation of the presence of this effect and a full reconstruction of the gas velocity pattern. The third and fourth works are oriented to the important question of complex plasma diagnostics by means of optical emission spectroscopy. The influence of micro particles on plasma parameters were shown by evaluation of metastable density and electron temperature.