Oh, rayon. Rayon is a tricksy fabric. Why? Because it can be made of wood, bamboo, or other plant materials, but is not considered a “natural fabric” (generally defined as a fabric that does not use synthetic materials to be created ex. silk, wool, cotton). Instead, it is defined as a “regenerated cellulose”. Cellulose refers to the plant materials it uses as its base, regenerated refers to the fact that extensive chemicals are used to break down then build up the cellulose before it can be a fabric.
Rayon goes through a long list of steps to come into existence. A short version is…get your raw materials (cellulose), soak it in several chemicals (separately), age it, filter it, then spin it into rayon filaments. These filaments are then knit or woven into fabric. You can check out the details on Wikipedia, or wisegeek. Unfortunately, even though rayon comes from natural materials, the processes it goes through can really pollute the environment around the areas it is made.
Rayon is the oldest manufactured fabric and was originally conceived as an alternative to silk. It drapes wonderfully and is generally cheaper than silk. Also, it dyes better than most materials. Rayon can be silky, shiny, chunky, nubby, soft, crisp, thick, transparent…it is a truly versatile fabric!
Pros: soft, versatile, has roots in natural materials, dyes like the dickens, drapes like a second skin
Cons: not as eco-friendly as it first appears, easily stained and takes a higher level of care to keep nice, factories that produce it need to be vigilant in its waste removal and processing