HIER involves heating tissue sections in a specific retrieval solution, usually using a [microwave](https://), pressure cooker, or water bath. The retrieval solution is typically a buffered solution with a specific pH, such as citrate buffer (pH 6.0) or Tris-EDTA buffer (pH 9.0). The heat and buffer work together to break the cross-links formed during fixation, thereby exposing the hidden epitopes.
