Optical microscopy afforded additional structural information (Figure ). The overall appearance of the double-decker flowers is very uniform. Varying the focal plane revealed that (i) the hexagonal core is continuous from the top to the bottom of the structure, (ii) the petals have a dendritic appearance, and (iii) there is a high degree of similarity between the two decks (as observed by SEM). We noted that the flowers consist of smaller flowers that embed the hexagonal core (width ≈ 10 µm) inside it (Figure ).