Simply stated, dyes are substances capable of imparting color by chemically or physically binding with materials (including biological tissues). This ability is due to the presence of color-bearing chemical groups called chromogens.
For tissue staining to occur, chromogens in a dye solution must bind to the desired elements through one of two processes:
- Absorption: A physical process by which the dye dissolves directly into desired elements in the sample.
- Adsorption: A chemical process by which the dye binds to elements in the sample that have an affinity (chemical attraction) for the dye.
