For the first time in more than three centuries, Prussian Blue – long confined to its rigid cubic shape – has been transformed into an octahedral structure. Schematic illustration of the particle formation mechanism of glycerol-based octahedral Prussian Blue POSTECHAccidentally discovered around 1700s, Prussian Blue possesses a hollow three-dimensional framework that allows ions to move in and out with ease. By using viscous glycerol instead of water, they were able to slow down crystal growth. When tested as an electrode material in sodium-ion hybrid capacitors, the octahedral Prussian Blue demonstrated remarkable advantages. This study is the first to demonstrate that specific solvents can control both the growth rate and the orientation of Prussian Blue crystals.