The cell is the structural and functional unit of all living organisms. Cells with membrane-bound nuclei are called eukaryotic, whereas cells that lack a membrane-bound nucleus are called prokaryotic. In both eukaryotic and prokaryotic cells, a semi-fluid matrix called cytoplasm occupies the cell's maximum volume. In eukaryotes, there is extensive compartmentalization of cytoplasm. The cytoplasm is the main arena of cellular activities in both plant and animal cells.