Optical magnetic twisting cytometry and traction force microscopy are two advanced cell mechanics research tools that employ optical methods to track the motion of microbeads that are either bound to the surface or embedded in the substrate underneath the cell. The former measures rheological properties of the cell such as cell stiffness, and the latter measures cell traction force dynamics. Here we describe the principles of these two cell mechanics research tools and an example of using them to study physical behaviors of the living cell in response to transient stretch or compression. We demonstrate that, when subjected to a stretch-unstretch manipulation, both the stiffness and traction force of adherent cells promptly reduced, and then gradually recover up to the level prior to the stretch. Immunofluorescent staining and Western blotting results indicate that the actin cytoskeleton of the cells underwent a corresponding disruption and reassembly process almost in step with the changes of cell mechanics. Interestingly, when subjected to compression, the cells did not show such particular behaviors. Taken together, we conclude that adherent cells are very sensitive to the transient stretch but not transient compression, and the stretch-induced cell response is due to the dynamics of actin polymerization.