What does a secondary stain do in the staining procedure?

In the staining procedure, a secondary stain refers to the stain that is applied after the primary stain. The purpose of the secondary stain is often to enhance the visibility of different cellular structures or to differentiate between various components of a sample. This is particularly important in techniques like Gram staining, where the primary stain characterizes the overall group of bacteria, and the secondary stain provides additional color contrast to elucidate details that the primary stain alone might not reveal.

By applying a secondary stain, specific features of the cells or tissue can be highlighted, allowing for better observation and analysis under a microscope. This technique is crucial in histology and microbiology for identifying and differentiating between different types of cells, bacteria, or tissue structures, making the secondary stain an essential part of the staining process.