The plasma membrane is a dynamic structure with roles in maintaining cellular form, providing a barrier, and regulating various cellular processes, including immune receptor signaling responses. Unlike a simple lipid complex, the plasma membrane has a dynamic structure influenced by diverse lipid interactions, membrane proteins, and cytoplasmic structures. Comprising outer and inner leaflets, the membrane exhibits variations in lipid composition between cell types, with a prevalence of saturated lipids in the outer leaflet and unsaturated lipids in the inner leaflet. Studies on red blood cells and mast cells confirm this asymmetry, with the outer leaflet resembling a liquid-ordered phase and the inner leaflet a liquid-disordered phase. This lipid distribution can undergo phase-like segregation triggered by external stimuli. The membrane's physical properties contribute to the activation and control of cellular activities. In the context of FcεRI signaling in mast cells, the spatial organization of membrane components, influenced by lipid properties, plays a crucial role. Research involving various biophysical and molecular biology tools has explored membrane interactions and dynamics in resting and antigen-stimulated conditions. Techniques like TIRFM-based ImFCS and FRAP reveal changes in diffusion properties of membrane components. The plasma membrane tends to adopt a more liquid-ordered state after antigen stimulation, emphasizing Lyn's role in initiating downstream signaling events. Chapter 2 delves into inter-leaflet coupling, crucial for maintaining membrane equilibrium and regulating signaling processes. The inner leaflet lacks significant lipid order in its resting state, proposing that inter-leaflet coupling induces ordering after stimulation. A method involving lipid exchange on the outer leaflet demonstrates a correlation between outer leaflet lipid composition, inner leaflet order, and cellular responses to FcεRI signaling. Chapter 3 introduces ImFCS to monitor the time-dependent progression of membrane probe diffusion properties during intracellular responses. Comparisons between changes in diffusion coefficients and cellular responses indicate that the initiation of intracellular signaling precedes extensive lipid reorganization. Quantitative characterization of plasma membrane properties provides insights into how the membrane maintains a resting state and responds to external stimuli. The thesis introduces a new technique, boxcar ImFCS, for high time-resolution measurements, offering valuable information for understanding plasma membrane reorganization and its role in cellular responses.