The structure that controls the movement of materials into and out of all cells is the cell membrane (also called the plasma membrane).

Here's why:

* Barrier: The cell membrane acts as a barrier between the cell's internal environment (cytoplasm) and the external environment.

* Selective Permeability: It's selectively permeable, meaning it allows some substances to pass through while blocking others. This selectivity is crucial for maintaining the cell's internal environment.

* Transport Mechanisms: The cell membrane has various transport mechanisms, including:

* Passive transport: Movement of substances across the membrane without requiring energy (e.g., diffusion, osmosis).

* Active transport: Movement of substances against their concentration gradient, requiring energy (e.g., pumps, endocytosis, exocytosis).

In summary, the cell membrane plays a vital role in regulating what enters and leaves the cell, ensuring its proper function and survival.