Glia or glial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system. In the human brain, glia are estimated to outnumber neurons by about 10 to 1.

Glial cells provide support and protection for neurons. They are thus known as the "glue" (meaning of glia) of the nervous system. The four main functions of glial cells are to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy pathogens and remove dead neurons.

Some scientists, like Roger Penrose, think that consciousness lies on the microtubules of the glia, being each cell analogue to a computer and the neuron analog to a local area network. The whole nervous system would be a World Area Netword (WAN).