3.2 Bright Field Microscopy

Figure 3.7: H&E Stained Kidney Cells Viewed with Bright Field Microscopy

In this kind of microscopy, bright light is used to visualize samples. Such visualizations are based on the absorption of certain wavelengths of light.

3.2.1 Preparing a Sample for Light Microscopy

Figure 3.8: A Microtome Machine

There are three main steps:

1. Fixation

   This kills and preserves cells. Formaldehyde is commonly used.

2. Embedding and Sectioning

   The fixed tissue is dehydrated and embedded in hot wax or resin.

   This practice increases the mechanical strength of the tissue for sectioning (about 5 - 15 micrometers thick).

3. Staining

   This rehydrates the sample - various staining techniques can be used to reveal cellular and subcellular structures (e.g., organic dyes, H&E staining, etc).

3.2.2 H&E Staining

Figure 3.9: H&E Staining

This is a common technique in histology that uses two dyes: hematoxylin and eosin.

Nobody really knows the mechanism behind this staining just yet, but hematoxylin has an affinity for negatively-charged molecules.