Clusters of gray matter that contain neuron cell bodies and lie within masses of white matter are the

Cerebral Nuclei.

Explanation:

Cerebral nuclei refers to one of three components of the cerebrum. It is a composite structure of the end-brain defined on the basis of origin from the ventricular ridge of the embryonic Encephalon. It is a lusters of gray matter that contain neuron cell bodies and lie within masses of white matter.

when a reversible reaction is occurring in both directions at the same rate; the products and reactants do not change in concentration. a chemical reaction where the compound is broken into its constituent parts.