Radiofrequency systems are able to emit energy that transforms into thermal energy as it passes through the body tissues (this happens only if the emission frequency is between 1MegaHz and 10 Giga Hz). Different types of tissue and their components present different resistance and therefore the heat generated is different. The energy passes through the first layers of the skin, leaving them unaffected, and mainly takes effect in the deeper layers of the skin. The heat generated by this method causes denaturation of the collagen which contracts, becoming shorter and thicker. This contraction is particularly evident in the fibrous septa that pass from the skin down to the underlying muscle, traversing the subcutaneous fat inbetween. Skin laxity is partly caused by the laxity of these fibrous septa, and so their contraction causes a noticeable improvement in the more superficial layers of the skin. The heat generated also stimulates collagen production by the fibroblasts. The areas treated are the lower third of the face, abdomen, arms, inner thighs, and the neck (except the area above the thyroid gland).