During tissue formation and wound healing, cells are exposed to mechanical stress. However, the molecular mechanisms that cells use to withstand tensile force are not completely understood. A key protein that is involved in sensing mechanical perturbations and transmitting it within the cell is the cadherin family of cell-cell adhesion proteins. My group has used single molecule force measurements and single molecule fluorescence imaging to identify how cadherins withstand tensile force and tune the mechanical properties of intercellular junctions. I will show that cadherins form three types of adhesive bonds: catch bonds which, counter-intuitively, become longer lived and lock in the presence of tensile force, slip bonds which become shorter lived when pulled and ideal bonds that are insensitive to mechanical stress. I will also describe a new technique that we invented to image fluorescent cadherins with nm accuracy and precision.