Glasses are solid materials that are far from their thermodynamic equilibrium states and their stabilities play a role in many applications as well the theoretical understanding of the natures of glass systems. Recently, ultrastable glasses (SGs) have been developed. The SGs have the stabilities that ordinary glasses can obtain only after being annealed for thousands to millions of years, thereby providing a great opportunity for studying the stabilities of glasses. In this paper we present a brief review about the properties of SGs and their formation mechanisms and novel insights into the glassy physics.