Fibroblasts support a broad range of essential organ functions via microarchitectural, biomechanical, and biochemical cues. Despite great advances in fluorescence, photoacoustic conversion, and Raman scattering over the past decades, their invasiveness and limited spatial resolution hinder the characterization of fibroblasts in a single cell. Here, taking mouse embryonic fibroblasts (MEFs) as an example, we propose a novel noninvasive approach to investigate the compositional distribution of MEFs at the single-cell scale via terahertz (THz) nanoscopy. Compared to the topological morphology, THz nano-imaging enables the component-based visualization of MEFs, such as the membrane, cytoplasm, nucleus, and extracellular vesicles (EVs). Notably, we demonstrate the real-space observation of the influence of rapamycin treatment on the increase of EVs in MEFs. Moreover, the line-cut and area-statistical analysis establishes the relationship between the topological morphology and the THz near-field amplitudes for different cellular components of MEFs. This work provides a new pathway to characterize the effects of pharmaceutical treatments, with potential applications in disease diagnosis and drug development.