In this episode of Deep Dive (Science Edition), we unpack how nature builds and protects our bones and teeth using a remarkably elegant materials science playbook. Drawing on the review “A materials science vision of extracellular matrix mineralization” by Reznikov, Steele, Fratzl, and Stevens, we explore how the body turns everyday ions like calcium and phosphate into tiny, imperfect crystals that make skeletons both strong and tough—while cleverly preventing dangerous crystal buildup in soft tissues like arteries. We explain why bones are pre-stressed like reinforced concrete, how “helper” and “blocker” molecules choreograph where minerals can and can’t grow, and why small, flawed crystals actually make bones safer and more resilient. We also look at what goes wrong in aging and disease when this balance slips, how that leads to vascular calcification, and how engineers are learning from nature—using enzymes, smart scaffolds, and subtle surface cues—to repair or replace mineralized tissues. Finally, we spotlight cutting-edge microscopes and imaging that let scientists watch minerals form in real time, and the big open questions that could reshape future therapies.