An introduction to ferrofluids in MEMS applications is presented. Ferrofluids are fluids with magnetic properties. By applying a magnetic field, the balance of forces within the ferrofluid is varied so that the magnetic fluid can move or apply pressure. These capabilities can be used in the field of the microsystems. In this work, we have obtained the typical values of pressure which can be expected from a ferrofluid. Using a piezoresistive pressure sensor, a pressure of 0.04 bar has been obtained.