An Object filled with tiny particles. Rendered with specular shading and high density.
Scene File for XSI 7.0+

Particle cache loader with enabled Trail feature.

Particles with a color gradient and fractal noise textures.

A particle simulation with applied volume distortion.

Shape Texture applied with the flow feature, particle gradient used for the color.

Particles textured with a fractal.

Particle "bubble density" in combination with metaball density.

One fractal for the shape, shadow adjustment feature was used.

A simple perlin noise drives the density of the solid volume shader.

Volume texture shader with the feature to span coordinates between objects.

Making of a sky (11 min). Please right-click and download.