(In the USA viscose is called rayon if it's made into a fabric.)
Viscose is made from wood pulp (and also from soy, hemlock, bamboo, and sugar cane). It's therefore a natural fibre, and biodegradable (silverfish will eat it if they're hungry).
On the other hand, to get from wood to fabric you have to go through a lot of processes, and use a lot of water and chemicals (caustic soda, ammonia, acetone, sulphuric acid), so it's not necessarily as completely environmentally friendly as the manufacturers would like us to think.
Having said that, there's a new way of making viscose called the Lyocell process, which is environmentally better.
Viscose is a process, as well as a product, and viscose-made products include cellophane, synthetic sponges, sausage skins, and tea bags:
Not many of us get through a day without it, do we?
Spot The Frippet: viscose. The name of the substance comes from part of the process of making the stuff. It's complicated: wood chips are chemically dissolved to a pulp, then more chemicals dissolve the pulp to a fluid which is rolled into sheets, dried, shredded, treated, dissolved again to make it into a very thick (that is, viscose) fluid, which is then filtered, degassed, and then forced through small holes (in a thing called spinneret) to make threads.
The word viscose comes from the Latin viscōsus, which means full of bird-lime or sticky, from viscum, which is birdlime or mistletoe.