Harvested stem cells are activated by treating them with an amplitude modulated laser beam having a wavelength lying in the range of 405 to 980 nanometers. The frequency of the laser beam is modulated within a range of 8 to 12 MHz. Using the activated stem cells, tissue can be repaired and regenerated by preparing the unactivated stem cells, treating the unactivated stem cells with an amplitude modulated laser beam having a pre-determined frequency for obtaining activated stem cells, administering the activated stem cells into a body containing the tissue, and using a homing beam to guide the activated stem cells within the body to the location of the tissue.