I. Chemical Systems
 

a) Chemical waves in the Belousov-Zhabotinsky reaction
Wave structures in a petri dish (target pattern and a counterrotating double spiral).	Spirals on a nonuniformly curved surface.
Spirals on hemispherical shells with different radii.	Wave structures in a weakly excitable medium induced by a defect.
Drift of a spiral core under feedback-controlled forcing (Creation of a resonance attractor).	"Chemical Canyons"  3D graphic representation of an excitation wave pattern.
Visualization of a "resting" spiral core by superposition of six pictures during one rotation.	"Chemical Tornado"  Spiral core in 3D perspective.
b) 3D structures
Tomographic reconstruction of a three dimensional scroll wave (i.e. a cylindric continuation of a spiral).  Top: Enlargement of the picture in the center  Bottom: Time series of a scroll wave  Left: Initial scroll wave, slightly twisted  Middle and right: Rest of a scroll wave, sending out plane wave fronts
c) Stationary structures in an autocatalytic reaction
"Pinstriped" activation centers in the methylene blue-oxygen-sulfite reaction.	"Honeycomb" pattern in the methylene blue-oxygen-sulfite reaction in a polyacrylamide gel.
d) Front  instability
Instability of an autocatalytic front leads to complex spiral pattern (numerical simulation).	Density driven convection deform a rising reaction front into a fingering structure.

II. Biochemical Systems
 

Biochemical example of an excitation front, observed during the glycolysis in cytoplasm extracted of yeast cells.	Circular waves during the glycolysis in cytoplasm extracted of yeast cells.
Spiral waves of NADH during the glycolysis in cytoplasm extracted of yeast cells.	Spiral waves of H^+ during the glycolysis in cytoplasm extracted of yeast cells.

III. Biological Systems
 

a) Spiral waves in biological systems
Spiral-shaped propagation of “Spreading Depression” in neuronal tissue, here on the chicken retina.	A sequence of superimposed pictures indicates the Z-shaped geometry of the spiral core.
Spiral geometry of a signal transmitter in an amoeba population (Dictyostelium discoideum) leads to chemotactic movements of cells in direction of the spiral core.	In the area of the spiral core of an amoeba population many single cells flow together in a vortex-shaped movement. This results in the growth of a multicellular organism.
b) Stationary bands in Characean algae cells
Stationary distribution of alkaline and acid regions around an illuminated Chara cell. The pattern was visualized using phenol red. Red spots correspond to alkaline regions.

IV. Some more spirals
 

Lichen in the tundra.	Rayleigh-Bénard convection. In SF6 near the gas-liquid critical point.
Helicoidal Liesegang precipitation band of PbI2 in agar.	Spiral galaxy NGC 1232.
Spiral formation on the surface of a growing cell (K. Wada, 1966)

V. Structural Similarity
 

Hydrodynamical convection rolls.	Surface of a coral.
Salt formation in the Atacama desert.	Mushroom spore (M. Ebert, Umweltmineralogie, TU Darmstadt).
Fingers of solidified lava in the Teide mountains, Las Canarias, Tenerife (photo by M. Böckmann)

VI. In the Laboratories
 

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