Scanning electron microscopy (SEM) analysis shows that gel G1 (see ESI S31-S32) is composed of lightly curved fibers intersecting to form a network of wires, with thicknesses ranging from tens to hundreds of nanometers, covered by a thick layer of amorphous material. In contrast, gel G2 (see ESI S33) is made of thicker rods (hundreds of nanometers) coated with a thinner layer of amorphous material. When the metastable gels transform into their thermodynamically stable forms (D1 or D2), the lightly curved fibers of G1 become straight rods up to 2 μm thick (see ESI S34-S35).