Not to be confused with intercellular, meaning "between cells".
In cell biology, molecular biology and related fields, the word intracellular means "inside the cell".[1]
It is used in contrast to extracellular (outside the cell). The cell membrane (and, in plants, the cell wall) is the barrier between the two, and chemical composition of intra- and extracellular milieu can be radically different. In most organisms, for example, a Na+/K+ ATPase maintains a high potassium level inside cells while keeping sodium low, leading to chemical excitability.[2][3] This terms also means existing within the cells.