Traditional tissue analysis destroys spatial context. Bulk methods–Western blots, ELISA, flow cytometry–homogenize tissue, measuring average molecular abundance across all cell types and regions.
This averaging obscures clinically relevant biology. The tumor invasive margin may have different checkpoint engagement than the tumor core. Immune-rich "hot" regions may show different PPILoading... patterns than immune-excluded "cold" regions. Heterogeneity is the rule, not the exception.
Spatial biology preserves tissue architecture, enabling molecular analysis at single-cell or subcellular resolution while maintaining spatial relationships. The question shifts from "what's the average?" to "what's happening where?"