The Relativistic Heavy Ion Collider (RHIC) is a versatile machine that has provided collision between a wide range of heavy ions, from d to Au, as well as proton+proton and proton+nucleus collisions. Polarized proton program at RHIC provides unique testing ground for the fundamental study of the proton's spin structure. The large transverse single spin asymmetry (TSSA) in pion production in high energy polarized proton+proton reaction was discovered almost 3 decades ago and the origin of the asymmetry is the one of the long standing open questions in QCD as of now. The latest highlights from the PHENIX experiment addressing the transverse spin structures of proton and some results from polarized proton at $¥sqrt{s}=200$ GeV using various observables in wide rapidity region are discussed in this report. In addition, the latest TSSA results from transversely polarized proton+nucleus collision from Run15 are presented. Possible mechanism of rather unexpected large A-dependence in (very) forward rapidity region is addressed as well.