Through structure simulations ranging from ab-initio molecular dynamic simulations to million-atom-simulations we explore the structure of SiCO ceramics with a focus on its “free” carbon phase. "Free" carbon is embedded in and surrounded by the glass network and develops through distinct stages. Initially, carbon appears in isolated units and well dispersed throughout the material – reminiscent of the polymer precursor used in synthesis. During pyrolysis, carbon fragments combine to larger finite segregations of single-layered carbon sheets. Depending on the relative amount of "free" carbon, the segregations encase the surrounding SiCO glass matrix into small domains. Further annealing creates tubular carbon structures, which, ultimately, convert into large graphitic segregations.