Over the last years, hyaluronic acid (HA) injectable dermal fillers (DFs) have become the most popular agents for soft tissue contouring and volumizing. HA fillers are characterized by most of the properties that an ideal DF should have, due to HA unique chemical-physical properties, biocompatibility, biodegradability, and versatility. Therefore, HA DFs have revolutionized the filler market with a high number of products, which differ in terms of HA source, cross-linkage (agent and degree), HA concentration, hardness, cohesivity, consistency, inclusion or lack of anesthetic, indication, and longevity of correction. The article first provides a general introduction to DF world, and an overview of the different materials is available for fillers. Second, it describes the characteristics and the peculiarities of HA fillers, their differences from the other available materials, and therefore the reasons at the base of their success. Moreover, an update regarding the main Food and Drug Administration (FDA) approved fillers is presented.