To make salt water a heterogeneous mixture, you would have to

Salt water is made by mixing salt (NaCl) in water. It is a homogeneous mixture and a heterogeneous one. A difference between the two is that concentration is same everywhere in case of a homogeneous mixture, whereas, in case of a heterogeneous mixture, the concentration varies from place to place within a mixture.

Explanation:

Homeostasis = the tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.

More simply, homeostasis can be described as equilibrium or balance in the body.