Fig. 1. Artificial crystals: (a) Single crystal of K₃Ba₃Li₂Al₄B₆O₂₀F^[1]; (b) crystal of NH₄B₄O₆F^[3].

Fig. 2. (a) From the nanoscale of protein molecules to the macroscopic scale of physiology, the hierarchical structure of bone has significant characters of strong toughness and impact resistance^[4]; structures found on surfaces of plants and animals (b)−(e) and biomimetic, particle-based microstructures (b')−(e')^[5]: (b) the antireflective wings of a cicada^[6]; (c) the superhydrophobic leaves of taro^[7]; (d) lenses in the peripheral layer of the dorsal arm plate of a brittle star^[8]; (e) the corneal nipple arrays of a peacock butterfly^[9]; (b') antireflective silicon cone arrays^[10]; (c') superhydrophobic, raspberry-like arrangements^[11]; (d') micro-lenses from calcium carbonate (that show the magnified letter “A” here)^[12]; (e')superhydrophilic, self-cleaning titania nanocolumns^[13].

Fig. 3. Structure color and photonic crystals: (a) The blue iridescence and SEM image of the 1D structure of the Morpho butterfly; (b) multi-coloured peacock feather and TEM image of transverse cross section of the 2D structure of the blue area of a wing; (c) wing of the male Sasakia Charonda butterfly and SEM image of the 3D structure of the white iridescent area^[18]; (d) schematic drawings of the structures of 1D, 2D, and 3D photonic crystals^[19].

Fig. 4. Artificial structure color: (a) SEM images of binary opal films formed by large 850 nm silica spheres packed in interstices^[21]; (b) SEM images of binary opal films formed by small 150 nm polystyrene latex spheres packed in interstices^[21]; (c) SEM image of two-dimensional colloidal crystal formed by silica microspheres; (d) wafer-scale colloidal crystal film shown in figure (c)^[22].

Fig. 5. Active structure: (a) Reversible color change is shown for the leopard chameleon exposed to external stimuli (white arrow) through adjustments of micro-nano structures on skin surface; (b) TEM images of guanine nanocrystals in S-iridophores in the excited state and three-dimensional model of an FCC (face-centered cubic) lattice (shown in two orientations). Scale bar: 20 μm^[23]; (c) cell membrane is a double-layer membrane structure composed of phospholipid molecules, which is highly deformable and adaptable^[25]

Fig. 6. Non-equilibrium self-organizations in nature: (a) The formation of Bernard convection pattern^[26]; (b) cytoske-leton^[27]

Fig. 7. Collective motions in natural and colloidal systems: (a) Schooling of fishes; (b) flocking of birds^[32]; (c) swimming bacillus subtilis bacteria^[33]; (d) a roller vortex with circular restricted boundary. The blue vectors represent instantaneous speed of the rollers^[49]; (e) directed collective motion of colloidal rollers. The blue arrows represent the instantaneous particle velocities^[50].

Fig. 8. Dynamic self-assembly in the colloidal systems: (a) Self-assembled multi-segment snake-like structures generated by a vertical alternating magnetic field. The size of the segments is determined by the magnetic field frequency^[53]; (b) living crystals assembled from a homogeneous distribution under illumination by blue light; (c) living crystals melt by thermal diffusion when light is extinguished^[32]; (d) optical micrographs of staggered chains (56 V·cm^–1 at 40 kHz) of Janus particles in an alternating-electric field^[54]; (e) optical micrographs of concentrated staggered chains (27 V·cm^–1 at 40 kHz) of Janus particles in an alternating-electric field^[54].

Fig. 9. (a)−(h) Spot diagrams of vibration granular surface forms: Experiment and simulation results (Γ is acceleration and is frequency)^[55].