Here's a breakdown of its key features:

* Double-walled: It's composed of two layers of phospholipids, arranged with their hydrophilic heads facing the watery environments inside and outside the cell, and their hydrophobic tails tucked in between.

* Hydrophobic tails and hydrophilic heads: This structure is crucial for the membrane's function. The hydrophobic tails repel water, while the hydrophilic heads attract it. This arrangement creates a barrier between the cell's interior and the external environment.

* Found in all cells: The cell membrane is a fundamental component of all living cells, from bacteria to plants and animals.

* Controls what enters and leaves the cell: The cell membrane acts as a selective barrier, regulating the passage of molecules into and out of the cell. This is essential for maintaining the cell's internal environment and carrying out its functions.

Let me know if you'd like to learn more about specific aspects of the cell membrane, like how it transports molecules or the types of proteins embedded within it!