A method of preparing a population of stem cells for autologous implantation to a subject and apparatus used therein are provided. The cells are activated by irradiating the cells with one or more wavelengths of yellow and red and/or green light. In particular, the cells are irradiated with 575-595 nm (5-20 mW), and 630-635 nm or 660-670 nm (10-100 mW) and/or 510-540 nm (10-60 mW) of monochromatic light for 30-60 mins. Preferably the stem cells are adipose-derived stem cells. Therapeutic applications of the activated stem cells are also provided.
