of their actin cytoskeleton. [5][6][7][8][9] Despite the significance for cell function, [10,11] our understanding of the interplay of cell mechanics and its underlying actin kinetics controlling the adaptive mechanical behavior of cells remains at best correlative from independent measurements.Fluorescence recovery after photobleaching (FRAP) is perhaps the most successful quantification methodology of molecule kinetics and dynamics, owing to its versatility to measure reaction and diffusion dynamics at the right spatiotemporal scales. [12][13][14] In a typical FRAP experiment, a small region of interest (ROI) is bleached by a short exposure to highpower laser light, and subsequently the recovery of fluorescently tagged molecules is monitored over time. [15][16][17][18] The shape of the FRAP recovery curve, the so-called mobile fraction, reflects all of the complexity of the reaction diffusion dynamics of the molecule of interest. Using a theoretical model or numerical simulations for the analysis of the molecular actions combined with knowledge of the recovery time(s) of the respective molecule, the reaction kinetics and diffusion dynamics can be calculated and interpreted. [19][20][21] Analysis of the experiments reveals whether a molecule undergoes reaction kinetics or diffusion dynamics or a combination of both processes. [13,22] The presence of a substantial immobile fraction may be the result of the loss of fluorescence due to imaging as experienced by the fluorescent molecules during image acquisition, or it may signify that recovery has been followed over a duration that is short in comparison with the molecule's actual recovery time. [13] To this end, FRAP has been employed to identify and quantify the different types of filamentous actin (F-actin), their turnover dynamics, and lengths in the actin cortex, lamellipodium, and stress fibers. [22][23][24][25][26] Atomic force microscopy (AFM) is the most broadly used quantification methodology of cell mechanics. AFM allows the precise quantification and application of mechanical forces on the apical cell surface with piconewton (pN) resolution. [27][28][29][30][31] For the application of mechanical force over a microscaled subregion of a cell, the cantilever tip is typically functionalized with a micron-sized fluorescent bead, and then exerted against the apical cell surface. Using AFM electronic feedback loops allows the recording of nanoscale force indentations of the cell surface as a function of the applied constant mechanical force. For example, this type of approach has been applied to investigate the biological behavior and function of living cells in response to external mechanical force. [32,33] Quantifying the adaptive mechanical behavior of living cells is essential for the understanding of their inner working and function. Yet, despite the establishment of quantitative methodologies correlating independent mea surements of cell mechanics and its underlying molecular kinetics, explicit evidence and knowledge of the sensitivity of the feedback me...