The study investigates the organization of cytoplasmic components in eukaryotic cells, focusing on the formation of mesoscale condensates (BMCs) that are smaller than the typically studied micrometer-scale assemblies. Using Xenopus egg extract, the researchers employed a combination of filtration experiments, quantitative proteomics, and size exclusion to reveal that at least 18% of the proteome is organized into mesoscale BMCs, with sizes around 100 nm. These BMCs are stabilized by RNA or gelation and exhibit liquid-like properties. The findings suggest that eukaryotic cytoplasm is extensively organized into BMCs at short length scales, challenging the conventional view of BMCs as large, membrane-less structures. The study also developed a method to predict proteins involved in LLPS (liquid-liquid phase separation) by integrating filtration data and sequence features, achieving an AUC of 0.93. Additionally, the research highlights the role of RNA in stabilizing these BMCs and suggests that the mesoscale organization is highly dynamic, reflecting continuous assembly and disassembly processes.The study investigates the organization of cytoplasmic components in eukaryotic cells, focusing on the formation of mesoscale condensates (BMCs) that are smaller than the typically studied micrometer-scale assemblies. Using Xenopus egg extract, the researchers employed a combination of filtration experiments, quantitative proteomics, and size exclusion to reveal that at least 18% of the proteome is organized into mesoscale BMCs, with sizes around 100 nm. These BMCs are stabilized by RNA or gelation and exhibit liquid-like properties. The findings suggest that eukaryotic cytoplasm is extensively organized into BMCs at short length scales, challenging the conventional view of BMCs as large, membrane-less structures. The study also developed a method to predict proteins involved in LLPS (liquid-liquid phase separation) by integrating filtration data and sequence features, achieving an AUC of 0.93. Additionally, the research highlights the role of RNA in stabilizing these BMCs and suggests that the mesoscale organization is highly dynamic, reflecting continuous assembly and disassembly processes.