Phospholipids (Phosphatidylcholine) are lipids that contain phosphoric acid and are complex lipids. Phospholipids are components of biological membranes and are divided into two categories: glycerophospholipids and sphingolipids. Phospholipids are amphipathic molecules with hydrophilic nitrogen- or phosphorus-containing heads at one end and hydrophobic (lipophilic) chains of long hydrocarbon-based groups at the other end.

Phospholipid ferric hematoxylin (FeH) staining solution was invented by Elleder, the principle is that phospholipids can be shown by trivalent ferric hematoxylin, the method is easier, faster and more sensitive than DAH, the disadvantage is that the tissues need to be degreased with acetone before the staining effect is good, and sometimes the cell nucleus and lipids are stained with black-blue color at the same time.