Two different types of experiments were performed. In the first experiment we studied the low-temperature condensation of vaporized graphite inside bulk liquid helium while in the second experiment the condensation of single carbon atoms together with H2, H2O, and CO molecules inside helium nanodroplets was studied. The condensation of vaporized graphite leads to the formation of partially graphitized carbon, which indicates high-temperatures, supposedly higher than 1000 °C, during the condensation. Possible underlying processes responsible for the instant rise in temperature during condensation are discussed. This suggests that such processes cause the presence of partially graphitized carbon dust formed by low-temperatures condensation in the diffuse interstellar medium. Alternatively, in the denser regions of the ISM, the condensation of carbon atoms together with the most abundant interstellar molecules (H2, H2O, and CO), leads to the formation of complex organic molecules (COMs) and finally organic polymers.Water molecules were found not to be involved directly in the reaction network leading to the formation of COMs. It was proposed that COMs are formed via addition of carbon atoms to H2 and CO molecules (C + H2 → HCH, HCH + CO → OCCH2). Due to the involvement of molecular hydrogen, the formation of COMs by carbon addition reactions should be more efficient at high extinctions compared with the previously proposed reaction scheme with atomic hydrogen.