DNA and ribonucleic acid (RNA) are nucleic acids. Alongside proteins, lipids and complex carbohydrates (polysaccharides), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life. DNA is a long polymer made from repeating units called nucleotides. Dermal fibroblasts are the major component of the skin; they not only serve as the building blocks of collagen, but also play a crucial role in the regulation of skin physiology. Polynucleotides promote the growth and activity of fibroblasts. Fibroblasts are located in the dermal layer, suggesting that polynucleotides must be administered directly into this layer to obtain maximum benefits.