Tissue Embedding Agents

Animal tissues are soft and are difficult to slice into thin sections. Embedding agents are used to make the tissue sufficiently hard. Paraffin embedding is commonly used in optical microscopy, and embedding in various resins is used in electron microscopy. Frozen sections are sometimes used instead of embedding. Fujifilm Wako offers Pathoprep, which is a purified paraffin with improved tissue permeability.

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Paraffin Embedding

Replacing the water in formalin-fixed tissue with paraffin makes the tissue sufficiently hard for sectioning. Paraffin sections offer excellent preservation and are used to prepare permanent specimens for optical microscopy. Another advantage is that relatively thin sections of 1-10 μm can be obtained. On the other hand, there are disadvantages in that the process of embedding may reduce antigenicity, and it is time-consuming. Fujifilm Wako offers Pathoprep, a purified paraffin with improved tissue permeability.

Resin Embedding

Various resins, including epoxy resins, are used as embedding agents for electron microscopy. The hardness of epoxy resin-based embedding agents can be adjusted by controlling the type and amount of curing agents, polymerization catalysts, accelerators, and other additives. The following properties are required for resins for embedding:

  • Does not shrink during polymerization
  • Monomers are easy to handle and readily penetrate tissues
  • Transparent and as colorless as possible
  • Polymers are resistant to electron beam
  • Polymers are easy to prepare with desired hardness
  • Easy to cut into thin sections


  1. Handbook for Staining and Bioimaging Experiments 5th ed.” ed. by Takata, K., Saito, N. and Kawakami, H., Yodosha, Japan, (2012). (Japanese)
  2. Okubo, K.: “Master of cell and tissue staining”, Yodosha, Japan, (2018). (Japanese)

For research use or further manufacturing use only. Not for use in diagnostic procedures.

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