Solar cells convert sunlight directly into electricity utilizing the photovoltaic (PV) effect. During the past few decades, PV has become a mature technology and created a large global industry. However, PV has to reach the terawatt scale in installed capacity to claim a significant share of the global energy supply and, thus, combat global warming. This chapter provides a brief introduction to various PV technologies and describes the current status of PV. Using specific examples and a simple cost model, challenges and opportunities for PV to become a pillar in a future, renewable energy-based system are discussed.