In recent years, tin perovskite solar cells have reached significant milestones, establishing themselves as the leading lead-free perovskite formulation, capable of matching or exceeding the efficiency and stability of lead-based perovskite solar cells. With a direct bandgap in the 1.3–1.4 eV range, this technology can surpass 30% in power conversion efficiency according to the Shockley-Queisser limit. However, several challenges are preventing this technology from realising its full potential. Tin’s tendency to oxidise from Sn2+ to Sn4+ leads to high bulk defect densities and recombination issues. The uncontrolled crystallisation resulting from Sn’s high reactivity can produce defective films with pinholes and poor morphology. Shallow energy levels and mismatches in energy with adjacent selective layers contribute to voltage (Voc) losses and induce instability. These three main challenges arise from the fundamentally higher reactivity of Sn2+ compared to Pb2+. This chapter provides a comprehensive overview of the current state of tin perovskite solar cells. We begin by clarifying the fundamental differences between tin and lead, followed by a detailed description of the main challenges in this field and strategies to mitigate them. The final section addresses the technological hurdles in developing tin perovskite solar cells, examining each challenge previously discussed from the perspective of photovoltaic applications.