This review provides a theoretical perspective on the glass transition in molecular liquids at thermal equilibrium, the spatially heterogeneous and aging dynamics of disordered materials, and the rheology of soft glassy materials. It begins with an introduction to the field, emphasizing its connections with other subjects and its relevance. The role of computer simulations in studying the dynamics of systems near the glass transition at the molecular level is highlighted. Recent progress on spatially heterogeneous dynamics, which characterize structural relaxation in materials with slow dynamics, is reviewed. The main theoretical approaches describing the glass transition in supercooled liquids are presented, focusing on those with a microscopic, statistical mechanics basis. Both successes and failures of these approaches are discussed, and their current status is critically assessed. The physics of aging dynamics in disordered materials and the rheology of soft glassy materials are then discussed, along with recent theoretical progress. For each section, the most recent advances are described, as well as important open problems that are expected to occupy a central place in this field in the coming years. The glass transition is not a thermodynamic transition but rather a phenomenon where the material becomes too viscous to flow on a reasonable timescale. A material is considered glassy when its typical relaxation timescale is of the order of, and often much larger than, the duration of an experiment or simulation. This definition applies to a wide range of systems, including liquids, hard condensed matter, charge density waves, spin glasses, and soft condensed matter. Glass physics covers a broad range of timescales and lengthscales, as illustrated in the figure. These materials exhibit glassy dynamics characterized by phenomena such as aging, hysteresis, creep, memory, effective temperatures, rejuvenation, dynamic heterogeneity, and non-linear response. The glass transition has broad implications, and glassy materials are found in many different physical situations. The study of glassy materials is motivated by their prevalence in everyday life and the theoretical challenges they present. The glass conundrum provides fundamental questions for theoretical physicists, as standard statistical mechanics tools are sometimes insufficient to account for the glass state. Simulating the dynamics of realistic materials on experimentally relevant timescales is also challenging. The field is constantly stimulated by new experimental developments that produce new types of disordered materials or provide more microscopic information on glassy systems. The review outlines the structure of the article, which includes a broad introduction to glassy materials, the issue of dynamic heterogeneity, main theoretical perspectives, aging and nonequilibrium phenomena, and general and concluding remarks. The article discusses the physical behavior of glassy materials, their relationships or empirical correlations, and the theoretical techniques and ideas developed in the field of spin glasses that are relevant to the glass transition. It also highlights the emergence of glassiness in other branches of science, such as computer science and neural networks, and the connection between optimization problems and glassy systems. The review emphasizes the importance of computer simulations in studying the glass transition and the challenges in understanding theThis review provides a theoretical perspective on the glass transition in molecular liquids at thermal equilibrium, the spatially heterogeneous and aging dynamics of disordered materials, and the rheology of soft glassy materials. It begins with an introduction to the field, emphasizing its connections with other subjects and its relevance. The role of computer simulations in studying the dynamics of systems near the glass transition at the molecular level is highlighted. Recent progress on spatially heterogeneous dynamics, which characterize structural relaxation in materials with slow dynamics, is reviewed. The main theoretical approaches describing the glass transition in supercooled liquids are presented, focusing on those with a microscopic, statistical mechanics basis. Both successes and failures of these approaches are discussed, and their current status is critically assessed. The physics of aging dynamics in disordered materials and the rheology of soft glassy materials are then discussed, along with recent theoretical progress. For each section, the most recent advances are described, as well as important open problems that are expected to occupy a central place in this field in the coming years. The glass transition is not a thermodynamic transition but rather a phenomenon where the material becomes too viscous to flow on a reasonable timescale. A material is considered glassy when its typical relaxation timescale is of the order of, and often much larger than, the duration of an experiment or simulation. This definition applies to a wide range of systems, including liquids, hard condensed matter, charge density waves, spin glasses, and soft condensed matter. Glass physics covers a broad range of timescales and lengthscales, as illustrated in the figure. These materials exhibit glassy dynamics characterized by phenomena such as aging, hysteresis, creep, memory, effective temperatures, rejuvenation, dynamic heterogeneity, and non-linear response. The glass transition has broad implications, and glassy materials are found in many different physical situations. The study of glassy materials is motivated by their prevalence in everyday life and the theoretical challenges they present. The glass conundrum provides fundamental questions for theoretical physicists, as standard statistical mechanics tools are sometimes insufficient to account for the glass state. Simulating the dynamics of realistic materials on experimentally relevant timescales is also challenging. The field is constantly stimulated by new experimental developments that produce new types of disordered materials or provide more microscopic information on glassy systems. The review outlines the structure of the article, which includes a broad introduction to glassy materials, the issue of dynamic heterogeneity, main theoretical perspectives, aging and nonequilibrium phenomena, and general and concluding remarks. The article discusses the physical behavior of glassy materials, their relationships or empirical correlations, and the theoretical techniques and ideas developed in the field of spin glasses that are relevant to the glass transition. It also highlights the emergence of glassiness in other branches of science, such as computer science and neural networks, and the connection between optimization problems and glassy systems. The review emphasizes the importance of computer simulations in studying the glass transition and the challenges in understanding the