 Biomolecular condensates are important for organizing cellular reactions, but their composition and structure have been difficult to study due to their small size and high density. This paper examined a mass density of four different types of condensates, finding that they all had lower densities than expected. The authors also found that these condensates were more permeable to proteins than expected, suggesting that they may be less dense than previously thought. Additionally, the authors observed that the presence of mitochondria affected how phase separation occurred, which could explain why some condensates are less dense than others. Overall, this paper provides new insight into the composition and structure of biomolecular condensates, providing valuable information on how they form and function. This article was authored by Tai Hume Kim, J. Unyo, Sung Go Do, and others.