Many varieties of layered inorganic-organic (IO) perovskite of type (where R: organic moiety, M: divalent metal, and X: halogen) were successfully fabricated and characterized. X-ray diffraction data suggest that these inorganic and organic structures are alternatively stacked up along -axis, where inorganic mono layers are of extended corner-shared octahedra and organic spacers are the bi-layers of organic entities. These layered perovskites show unusual room-temperature exciton absorption and photoluminescence due to the quantum and dielectric confinement-induced enhancement in the exciton binding energies. A wide spectral range of optical exciton tunability (350 to 600 nm) was observed experimentally from systematic compositional variation in (i) divalent metal ions (, , ), (ii) halides ( and ), and (iii) organic moieties (R). Specific photoluminescence features are due to the structure of the extended network and the eventual electronic band structure. The compositionally dependent photoluminescence of these IO hybrids could be useful in various photonic and optoelectronic devices.