Wool is a textile fibre produced by the shearing of sheep. The breed of the sheep, where it was raised, and how the fibre was treated after shearing can all affect the final characteristics of wool. While some is quite harsh and rough, other wool can be luxuriously soft and squishy. As a fibre, wool is very good at trapping heat, and is one of the few fibres that stays warm even when wet.

Silk is a natural protein fiber, produced by certain insect larvae when forming coccoons. The best known silk is obtained from the larvae of the mulberry silkworm. To produce 1 kg of silk, 104 kg of mulberry leaves must be eaten by 3000 silkworms. As a fibre, silk is smooth and soft, and it is one of the strongest natural fibres. It has excellent drape, but no elasticity the way that wool does.

Nylon is a synthetic material that is often used to provide structure, stability and strength to yarns made with other, softer fibres. A nylon content of at least 15% is recommended for socks.