The study presents the "SASP Atlas," a comprehensive proteomic database of soluble proteins and exosomal cargo from multiple senescence inducers and cell types, aiming to identify biomarkers of cellular senescence. The SASP, a complex secretory phenotype driven by senescent cells, has been linked to various age-related conditions. The authors used a label-free data-independent acquisition (DIA) mass spectrometry workflow to identify and quantify proteins secreted by senescent human lung fibroblasts and renal epithelial cells induced by X-irradiation, inducible RAS overexpression, and atazanavir treatment. They found that the SASP is highly complex and dynamic, with significant protein changes in response to each inducer. The study identified several candidate biomarkers of cellular senescence, including Growth/differentiation factor 15 (GDF15), stanniocalcin 1 (STC1), and serine protease inhibitors (SERPINS), which correlated with age in human plasma. The SASP Atlas will facilitate the identification of proteins characteristic of senescence-associated phenotypes and potential biomarkers for assessing the burden, origin, and tissue of senescent cells in vivo.The study presents the "SASP Atlas," a comprehensive proteomic database of soluble proteins and exosomal cargo from multiple senescence inducers and cell types, aiming to identify biomarkers of cellular senescence. The SASP, a complex secretory phenotype driven by senescent cells, has been linked to various age-related conditions. The authors used a label-free data-independent acquisition (DIA) mass spectrometry workflow to identify and quantify proteins secreted by senescent human lung fibroblasts and renal epithelial cells induced by X-irradiation, inducible RAS overexpression, and atazanavir treatment. They found that the SASP is highly complex and dynamic, with significant protein changes in response to each inducer. The study identified several candidate biomarkers of cellular senescence, including Growth/differentiation factor 15 (GDF15), stanniocalcin 1 (STC1), and serine protease inhibitors (SERPINS), which correlated with age in human plasma. The SASP Atlas will facilitate the identification of proteins characteristic of senescence-associated phenotypes and potential biomarkers for assessing the burden, origin, and tissue of senescent cells in vivo.