Older stuffed animals from grandparents' time were made from natural and biodegradable materials like cotton, wool, fur and felt on the outside and natural fibers like rags, wood shavings or kapok for stuffing. These toys would decompose over time without harming the environment. Today's plush toys, in contrast, break sustainability rules by being made almost entirely from polyester derived from non-renewable oil that does not degrade and pollutes the environment. Synthetic polyfill is also increasingly used for stuffing instead of natural materials.