  The measurement of phi mesons provides a unique and complementary method for
exploring properties of the hot and dense medium created in the relativistic
heavy ion collisions. It has a relatively small hadronic interaction cross
section and is sensitive to the increase of strangeness (strangeness
enhancement), a phenomenon associated with soft particles in bulk matter.
Measurements in the dilepton channels are especially interesting since leptons
interact only electromagnetically, thus carrying the information from their
production phase directly to the detector. Measurements in different
nucleus-nucleus collisions allow us to perform a systematic study of the
nuclear medium effects on phi meson production. The PHENIX detector provides
the capabilities to measure the phi meson production in a wide range of
transverse momentum and rapidity to study these effects. In this proceeding, we
present measurements of the phi mesons in a variety of collision systems at
$\sqrt{s_NN} = 200$ GeV. In case of small systems, the data are compared with
AMPT calculations to study the various cold nuclear medium effects involved in
phi meson production.
