We are very pleased to present this special section of the Journal of Biomedical Optics on hard tissue optics. Recent developments in lasers and other photonic technologies have enabled novel therapeutic and diagnostic applications targeted towards hard tissues. The chemical, structural, and mechanical properties of calcified tissues vary markedly from those of other biological tissues, leading to fundamentally different optical behavior. The differences are on display in the 10 papers included here. They report advances in dentistry (eight papers), urology (one paper), and orthopaedics (one paper).