Overview of the transformation of spongin scaffolds to a carbonized 3D structure at 1200°C. (A) Typical cellular and hierarchical morphology of Hippospongia communis demosponge organic skeleton after purification remains unchanged during the process of carbonization in spite of a decrease in volume by up to 70%. (B) Carbonized 3D scaffold can be sawn into 2-mm-thick slices (C). Stereomicroscopy (D and E) images of carbonized spongin network confirm its structural integrity, typical for sponge-like constructs.(F) NEXAFS C1s K-edge spectra of native and carbonized spongin heated at different temperatures, HOPG, and nanocomposite MWCNT/Cr2O3.