Cold laser units come in various sizes and shapes. Often the units used are handheld and similar to the size of an average flashlight. The treatment time required is usually dependent on two factors, the condition being treated and the size of the area affected. A major advantage of cold laser therapy units is the ability to penetrate deep into tissues and joints while retaining the capability to also treat conditions closer to the skin surface. People utilizing cold laser therapy as a non-invasive form of treatment report feeling little or no sensation during the treatment process. Regardless of how deep the light waves penetrate, the energy is eventually absorbed by the damaged cell providing it with the boost to begin working. Plants using the sun's light to stimulate growth and healing is a good analogy to demonstrate the effects of cold laser therapy. As these cells are repaired, the body is able to decrease the sensation of pain, reduce swelling, and accelerate the time required to heal.