The YK peptide also offers a platform for the bottom-up reconstitution of protein condensates in living cells. By building artificial protein condensates with different compositions or dynamic properties, we can evaluate the impacts on functions in living cells. This can contribute to the identification of factors essential for the biological functions involving protein condensates. Negatively stained TEM observation. YK13 peptide or YK13-sfGFP solutions were dropped on collodioncoated copper EM grids (Nisshin EM). For 60 s incubation, the solutions were removed and the grid surface was rinsed with filtered ultra-pure water. The YK13 peptide samples were stained by a 10% EM stainer (Nishin EM). The YK13-sfGFP samples were stained by Nano-W ® (twofold diluted), followed by rinsing with ultrapure water. All images were taken using a JEOL 1400Plus electron microscope.