Answer: Organelles
Step-by-step explanation:
Homeostasis can be defined as the process by which the organism maintain equilibrium inside its body despite of the changing environment outside.
The temperature, pressure, et cetera is maintained inside the body of organism which keeps the organism healthy.
In case of the single celled organism the pressure is controlled by the vacuoles which maintains the amount of water inside the organism. This is an example how the organism maintains homeostasis.