Iron(II) ferrocyanide, also known as Prussian blue, is a dark blue pigment made from the reaction of ferrous ions with ferrocyanide ions. It has the chemical formula Fe3[Fe(CN)6]2 and is commonly used in paints, inks, and as a dye due to its vibrant color and stability. This compound is notable for its ability to absorb toxins, making it useful in medical applications for treating heavy metal poisoning. Additionally, it has applications in photography and as a catalyst in various chemical reactions, showcasing its versatility beyond just a pigment.