Cavity optomechanics explores the coupling between optical and mechanical degrees of freedom via radiation pressure. This paper reviews the consequences of radiation pressure-induced back-action in whispering-gallery dielectric microcavities, focusing on two manifestations: parametric instability (amplification) and radiation pressure back-action cooling. Parametric instability offers a "photonic clock" driven by light pressure, while cooling surpasses cryogenic technologies, enabling phonon occupancies below unity and advancing cavity quantum optomechanics. The coupling arises from dynamic back-action, a classical effect due to finite cavity decay time, and has been observed in microtoroid cavities and other systems. Theoretical frameworks describe this coupling through coupled mode equations, showing how optical and mechanical modes interact. Dynamic back-action modifies mechanical dynamics, leading to mechanical amplification and cooling. The cooling mechanism, distinct from electronic feedback cooling, relies on radiation pressure-induced sidebands and has been experimentally verified. Theoretical models predict optimal detuning for maximum cooling or amplification, with cooling rates depending on cavity finesse and laser detuning. The study also highlights the importance of mechanical spectral selectivity, allowing targeted cooling of specific modes. Experiments demonstrate the effectiveness of dynamic back-action in cooling and amplifying mechanical oscillators, with applications in metrology and quantum technologies. The field is rapidly advancing, with potential for new quantum phenomena and practical applications in optomechanics.Cavity optomechanics explores the coupling between optical and mechanical degrees of freedom via radiation pressure. This paper reviews the consequences of radiation pressure-induced back-action in whispering-gallery dielectric microcavities, focusing on two manifestations: parametric instability (amplification) and radiation pressure back-action cooling. Parametric instability offers a "photonic clock" driven by light pressure, while cooling surpasses cryogenic technologies, enabling phonon occupancies below unity and advancing cavity quantum optomechanics. The coupling arises from dynamic back-action, a classical effect due to finite cavity decay time, and has been observed in microtoroid cavities and other systems. Theoretical frameworks describe this coupling through coupled mode equations, showing how optical and mechanical modes interact. Dynamic back-action modifies mechanical dynamics, leading to mechanical amplification and cooling. The cooling mechanism, distinct from electronic feedback cooling, relies on radiation pressure-induced sidebands and has been experimentally verified. Theoretical models predict optimal detuning for maximum cooling or amplification, with cooling rates depending on cavity finesse and laser detuning. The study also highlights the importance of mechanical spectral selectivity, allowing targeted cooling of specific modes. Experiments demonstrate the effectiveness of dynamic back-action in cooling and amplifying mechanical oscillators, with applications in metrology and quantum technologies. The field is rapidly advancing, with potential for new quantum phenomena and practical applications in optomechanics.