A system for light stimulation within a medium of a subject, comprising: a reduced-voltage x-ray source configured to generate x-rays from a peak applied cathode voltage at or below 105 kVp; a first plurality of energy-emitting particles for introduction in the medium, the first plurality of energy-emitting particles, upon radiation from the x-ray source, radiate at a first lower energy than the x-ray source to interact with at least one photoactivatable agent in the medium, wherein the first plurality of energy-emitting particles comprises at least one of: phosphor particles; ionic doped phosphor particles; single crystal or poly-crystalline powders; single crystal or poly-crystalline monoliths; fluorescent particles; scintillator particles; a metallic shell encapsulating at least a fraction of a surface of the particles; a semiconductor shell encapsulating at least a fraction of a surface of the particles; an insulator shell encapsulating at least a fraction of a surface of the particles; and quantum dots of a distributed size; wherein the system further comprises a mechanism to administer to the subject for the at least one photoactivatable agent at least one activatable pharmaceutical agent that is capable of activation a predetermined cellular change when activated, wherein light radiated from the first plurality of energy-emitting particles interacts with the at least one activatable pharmaceutical agent to activate the activatable pharmaceutical agent in situ, thus causing the predetermined cellular change to occur in the medium of the subject, wherein said predetermined cellular change treats the cell proliferation related disorder, wherein said photoactivatable agent is a psoralen. a reduced-voltage x-ray source configured to generate x-rays from a peak applied cathode voltage at or below 105 kVp; a first plurality of energy-emitting particles for introduction in the medium, the first plurality of energy-emitting particles, upon radiation from the x-ray source, radiate at a first lower energy than the x-ray source to interact with at least one photoactivatable agent in the medium, wherein the first plurality of energy-emitting particles comprises at least one of: phosphor particles; ionic doped phosphor particles; single crystal or poly-crystalline powders; single crystal or poly-crystalline monoliths; fluorescent particles; scintillator particles; a metallic shell encapsulating at least a fraction of a surface of the particles; a semiconductor shell encapsulating at least a fraction of a surface of the particles; an insulator shell encapsulating at least a fraction of a surface of the particles; and quantum dots of a distributed size; wherein the system further comprises a mechanism to administer to the subject for the at least one photoactivatable agent at least one activatable pharmaceutical agent that is capable of activation a predetermined cellular change when activated, wherein light radiated from the first plurality of energy-emitting particles interacts with the at least one activatable pharmaceutical agent to activate the activatable pharmaceutical agent in situ, thus causing the predetermined cellular change to occur in the medium of the subject, wherein said predetermined cellular change treats the cell proliferation related disorder, wherein said photoactivatable agent is a psoralen. phosphor particles; ionic doped phosphor particles; single crystal or poly-crystalline powders; single crystal or poly-crystalline monoliths; fluorescent particles; scintillator particles; a metallic shell encapsulating at least a fraction of a surface of the particles; a semiconductor shell encapsulating at least a fraction of a surface of the particles; an insulator shell encapsulating at least a fraction of a surface of the particles; and quantum dots of a distributed size; wherein the system further comprises a mechanism to administer to the subject for the at least one photoactivatable agent at least one activatable pharmaceutical agent that is capable of activation a predetermined cellular change when activated, wherein light radiated from the first plurality of energy-emitting particles interacts with the at least one activatable pharmaceutical agent to activate the activatable pharmaceutical agent in situ, thus causing the predetermined cellular change to occur in the medium of the subject, wherein said predetermined cellular change treats the cell proliferation related disorder, wherein said photoactivatable agent is a psoralen.