Abstract The Spatial Atlas of Human Anatomy (SAHA) is a foundational effort to map 250 million cells and transcriptomes and proteomes of 30 non-diseased organs from healthy adults at two spatial scales: whole transcriptome of histological features (50 µm to 2 mm), and 1,000-plex RNA and 64-plex protein panels at spatial subcellular resolution (50 nm across 1 cm2). The project aims to establish and validate best practices in experimental design, sample processing, data analysis, and data standards for high-content spatial analysis across multiple human organs at whole transcriptome and proteome levels. The profiled samples will capture variability across genders and ancestries. All results, including raw and processed data, will be made available to the scientific community through the SAHA data portal and AtoMxTM Spatial Informatics Platform. Here we present the part of Phase I data collected specifically around immune (bone marrow and lymph node) and gastrointestinal tissues (ileum, appendix, colon, and liver), and compare these data to colon and liver cancer samples. On serial sections, we perform spatial whole transcriptome data (with GeoMx® Digital Spatial Profiler) and 1,000-plex RNA profiles and 64-plex protein profiles collected by the CosMx™ Spatial Molecular Imager (SMI) matched to the exact shape of functional histological organ features from H&E and immunofluorescence stainings. Our data, which spans ~1.5 million cells collected across ~1,100 fields of view, enables the highest-ever subcellular resolution maps of cell types, lineage states, metabolic capacity, cellular neighborhoods, subcellular movements of organelles, and spatially resolved (and novel) ligand-receptor interactions across normal and cancer tissues. Through comparing these data to several cancer samples collected across multiple spatial platforms, we show how spatial organ atlasing at multiple scales can uncover unique insights into organ development, health, and cancer. We also show how the SAHA data can serve as a benchmark reference for spatial precision medicine. Citation Format: Jiwoon Park, Roberto Gregorio, Erika Hissong, Sanjay Patel, Brian Robinson, Fabio Socciarelli, Evenlyn Metzger, Yan Liang, Jason Reeves, Joseph Beechem, Olivier Elemento, Alicia Alonso, Shauna Houlihan, Robert Schwartz, Christopher E. Mason. Spatial Atlas of Human Anatomy (SAHA): A subcellular, multiscale spatial odyssey of immune and gastrointestinal tissues and tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4900.