1. Plasma Membrane: This is the outer boundary of the cell, acting as a selectively permeable barrier that controls what enters and exits the cell.

2. Cytoplasm: This is the gel-like substance that fills the cell, providing a medium for organelles to function and for chemical reactions to occur.

3. Genetic Material (DNA): This contains the cell's genetic instructions and guides all of the cell's activities. In eukaryotic cells, DNA is housed within a nucleus, while in prokaryotic cells, it is located in a region called the nucleoid.