Tin dioxide (SnO2), a semiconductor with a broad bandgap, has proved to be a multi-functional material of immense value across a broad spectrum of applications such as energy storage, environmental decontamination, gas detection, and advanced electronics. The current chapter gives review of the development in SnO2 synthesis methodologies from sol-gel and hydrothermal to green synthesis, their effect on structure, optical, and photocatalytic properties. Particular focus is placed on strategies of doping, morphological control, and nanostructure design that dramatically improve performance of SnO2 in catalytic and electronic applications. Incorporation of SnO2 makes them promising for next-generation sensing technologies, such as AI-enabled gas sensors, biosensors, and wearable devices, along with high-performance lithium/sodium-ion batteries, perovskite solar cells, and hydrogen production. Environmental uses, including wastewater treatment and self-cleaning surfaces, also illustrate SnO2 scope. In spite of promising progress, issues about stability, scalability, and eco-friendliness persist. The chapter ends with perspectives on future research directions centered on interdisciplinary integration, energy-efficient synthesis, and sustainable deployment of SnO2-based technologies.