Biological sample preparation requires adherence to strict standardized procedures. The fixation stage involves selecting appropriate fixatives such as paraformaldehyde or glutaraldehyde to ensure complete preservation of cellular structures. Dehydration employs gradient ethanol or acetone to gradually replace water in the sample. For embedding, choose suitable media: paraffin for optical microscopy, epoxy resin for electron microscopy. Time control and temperature management at each step directly impact final imaging quality.

Staining is crucial for enhancing sample contrast. Gram staining differentiates bacterial types, HE staining reveals tissue morphology, and immunofluorescence staining enables specific protein localization. When selecting staining methods, consider sample characteristics, observation objectives, and microscope type. Emerging quantum dot labeling technology provides more stable fluorescent signals for multicolor imaging.

Sectioning quality directly determines observation outcomes. Paraffin sections typically maintain 4-6 micron thickness, frozen sections 8-12 microns, and ultra-thin sections can achieve 50-70 nanometers. Ensure cutting blade sharpness and adjust appropriate sectioning speed and angle. Precisely control water bath temperature to prevent sample shrinkage or damage.

The entire sample preparation process requires strict environmental control. Temperature-sensitive samples should be handled at 4°C, enzymatic treatments at constant 37°C. Maintain humidity between 45%-65% to prevent sample drying or moisture absorption. Pay attention to time windows for each step, particularly fixation and staining durations, avoiding over- or under-processing.