Living cells respond to mechanical stimulation in a variety of ways that affect nearly every aspect of their function. Such responses can range from changes in cell morphology to activation of signaling cascades and changes in cell phenotype. Although the biochemical signaling pathways activated by mechanical stimulus have been extensively studied, little is known of the basic mechanisms by which mechanical force is transduced into a biochemical signal, or how the cell changes its behavior or properties in response to external or internal stresses. One hypothesis is that forces transmitted via individual proteins either at the site of cell adhesion to its surroundings or within the stress-bearing members of the cytoskeleton cause conformational changes that alter their binding affinity to other intracellular molecules. This altered equilibrium state can subsequently either initiate a biochemical signaling cascade or produce more immediate and local structural changes. To understand the phenomena related to mechanotransduction, the mechanics and chemistry of single molecules that form the signal transduction pathways must be examined. This paper presents a range of case studies that seek to explore the molecular basis of mechanical signal sensation and transduction, with particular attention to their macroscopic manifestation in the cell properties, e.g. in focal adhesion remodeling due to local application of force or changes in cytoskeletal rheology and remodeling due to cellular deformation.