The article provides a theoretical perspective on the glass transition in molecular liquids, 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 close to the glass transition at the molecular level is highlighted. The review covers recent progress in understanding spatially heterogeneous dynamics, which characterizes structural relaxation in materials with slow dynamics. It then presents various theoretical approaches to describe the glass transition in supercooled liquids, focusing on microscopic and statistical mechanics-based theories. 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 also explored, with recent theoretical advancements described. Each section includes an extensive overview of recent advances and identifies important open problems that are expected to be central in the field in the coming years.The article provides a theoretical perspective on the glass transition in molecular liquids, 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 close to the glass transition at the molecular level is highlighted. The review covers recent progress in understanding spatially heterogeneous dynamics, which characterizes structural relaxation in materials with slow dynamics. It then presents various theoretical approaches to describe the glass transition in supercooled liquids, focusing on microscopic and statistical mechanics-based theories. 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 also explored, with recent theoretical advancements described. Each section includes an extensive overview of recent advances and identifies important open problems that are expected to be central in the field in the coming years.