The eukaryotic cell is a multi-scale structure with modular organization across at least four orders of magnitude 1,2 . Two central approaches for mapping this structure -protein fluorescent imaging and protein biophysical association -each generate extensive datasets but of distinct qualities and resolutions that are typically treated separately 3,4 . Here, we integrate immunofluorescent images in the Human Protein Atlas 5 with ongoing affinity purification experiments from the BioPlex resource 6 to create a unified hierarchical map of eukaryotic cell architecture. Integration involves configuring each approach to produce a general measure of protein distance, then calibrating the two measures using machine learning. The evolving map, called the Multi-Scale Integrated Cell (MuSIC 1.0), currently resolves 69 subcellular systems of which approximately half are undocumented. Based on these findings we perform 134 additional affinity purifications, validating close subunit associations for the majority of systems. The map elucidates roles for poorly characterized proteins, such as the appearance of FAM120C in chromatin; identifies new protein assemblies in ribosomal biogenesis, RNA splicing, nuclear speckles, and ion transport; and reveals crosstalk between cytoplasmic and mitochondrial ribosomal proteins. By integration across scales, MuSIC substantially increases the mapping resolution obtained from imaging while giving protein interactions a spatial dimension, paving the way to incorporate many molecular data types in proteome-wide maps of cells.Advances in confocal microscopy and immunofluorescence (IF) imaging have created systematic pipelines for mapping the spatial distribution of proteins and other molecules within single cells 3,7,8 . Based on these techniques, the Human Protein Atlas (HPA) has launched an extensive effort to map protein subcellular locations using a library of specific fluorescent antibodies targeting more than 13,000 human proteins 5,9 . The use of multiple dyes with separate emission spectra enables locations to be determined relative to known landmarks such as the nucleus, cytoskeleton and endoplasmic reticulum, with the result that most human proteins can be assigned relative positions at sub-micron resolution.In parallel, advances in mass spectrometry (MS) have provided a complementary means of mapping protein coordinates through their biophysical associations with other proteins 4,10 . MS is now routinely combined with affinity purification (AP-MS) 11 or proximity-dependent labeling 12-16 to enumerate physical protein-protein interactions in vitro or in vivo. Combining AP-MS with epitope tagging, the BioPlex project has generated a systematic map of physical interactions covering approximately 7,500 epitope-tagged human proteins (BioPlex 2.0) 6 , including approximately 56,000 candidate interactions organized into more than 400 multimeric protein complexes.Given that protein imaging and biophysical association are leading approaches for mapping cell structure, with growing data resou...