The possible mechanisms of formation of PAHs and PANHs in different environments such as interstellar media under different ionizing conditions were investigated. Reactions of benzene radical cations with acetylene produce styrene and naphthalene-type cations at high temperatures are demonstrated. Ion molecule reactions of pyridine cation, benzonitrile cation and pyrimidine radical cation with acetylene are studied. Formation of complex organics with fused nitrogen atom in an aromatic ring is reported. Formation of PAHs over nanoparticle surfaces is carried out by studying polymerization of acetylene over Pd nanocatalyst and supported Pd nanocatalyst over MgO and CeO2 prepared by the LVCC technique under different temperature conditions are also reported in the book. Results of the ion-molecule reactions, associative charge transfer (ACT) and catalytic polymerization over catalysts surfaces' of acetylene interacting with different aromatic and heterocyclic cations could explain the different possible pathways of formation of complex organics in different ionizing environments in carbon-rich interstellar media in space.