The twenty-first century is marked by escalating environmental degradation and growing energy demands, driven by rapid industrialization, urban expansion, and unsustainable resource consumption. Climate change, pollution, biodiversity loss, and fossil fuel dependency are no longer isolated challenges but interconnected crises threatening ecological and human well-being. These global issues are compounded by inefficiencies in energy systems and disparities in energy access, calling for urgent and integrated solutions. This chapter lays the foundation for understanding how environmental and energy technologies play a transformative role in addressing these complex sustainability challenges. It presents an overview of major environmental and energy-related problems, followed by key technological responses ranging from pollution control, waste management, and resource efficiency to renewable energy systems, energy storage innovations, and smart grid solutions. The chapter also introduces micro- to nano-scale bio-based materials as emerging green technologies with promising applications across multiple sectors. It emphasizes the need for life cycle thinking, carbon footprint reduction, and alignment with Sustainable Development Goals (SDGs). Through a systems-oriented perspective, the chapter highlights how technological integration is essential to creating a resilient, low-carbon, and environmentally sustainable future.