Although hydrogen was firmly believed to be essential for the low-pressure synthesis, there have been a few reports, where diamond was synthesized in the absence of hydrogen. All the process of low-pressure diamond formation including the interstellar diamond dust have one common factor: presence of electric charge. The charged cluster model (J. Crystal Growth 62 (1996) 55) predicts that stabilization of diamond originates from charge rather than hydrogen. The diamond synthesis without hydrogen could be approached successfully by the charged cluster model.