  The PHENIX experiment at the Relativistic Heavy Ion Collider explores the
spin structure of the proton in polarized p+p collisions at center-of-mass
energies up to 500 GeV. Tremendous experimental and theoretical progress has
been made toward understanding the physics involved with transversely polarized
beams or targets in recent years. Not only nucleon structure and parton
distribution functions but also QCD dynamics have been studied in various
physics processes in high-energy polarized DIS and p+p collisions. In the 2006
and 2008 RHIC runs, the PHENIX experiment took a significant amount of
transversely polarized p+p collision data at 200 GeV center-of-mass energy,
with an integrated luminosity of 8 $pb^{-1}$ and beam polarizations up to 50%.
Single spin asymmetries of different probes have been measured in mid- and
forward-rapidities. In this report, we present the latest transverse spin
results from the PHENIX experiment and discuss briefly the prospects of future
transverse spin physics with the PHENIX detectors upgrades.
