All cells have at least three common features: a cell membrane, cytoplasm and DNA. Every cell has a selectively permeable cell membrane that allows some materials to pass in and out of the cell, and contains the water-based solution cytoplasm. Even if lacking a nucleus, all cells also contain DNA.
All living things are made up of cells. Cells are the basic structural unit for all organisms, according to cell theory. The main purpose of a cell in a larger organism is to organize. Humans are made up of hundreds of different types of cells. Plant cells have a cell wall of cellulose, which animal cells do not.