Here's why:

* Osmosis is the movement of water molecules across a semipermeable membrane from a region of high water concentration to a region of low water concentration.

* Hypertonic solutions have a higher solute concentration than the cell's internal environment. This means there's less water available outside the cell compared to inside.

* When a cell is placed in a hypertonic solution, water moves out of the cell to try to equalize the solute concentration. This causes the cell to shrink.

Let me know if you'd like more details on osmosis or types of solutions!