Brightfield cell counting is a method used to count cells in a biological sample. In this technique, cells are placed on a microscope slide and viewed under a brightfield microscope, which uses transmitted light to illuminate the cells. The contrast of the cells against the background of the slide makes it possible to count the number of cells in a sample. The cells appear as dark objects against a bright background, making it easier to distinguish individual cells and accurately count them. This method is widely used in cell biology and pathology, especially in cell counting and quantification of cell populations in cell cultures, blood smears, and tissue sections.

The process of brightfield cell counting involves preparing a sample of the cells on a microscope slide and staining them with a contrast agent, such as a dye, to make them more visible. The slide is then placed under the microscope, and the cells are counted using the eyepiece or a camera attached to the microscope.

Brightfield cell counting is a simple and cost-effective method for counting cells, but it has some limitations. For example, it can be challenging to accurately count cells that are tightly packed together, and the method is subjective, as the counts can vary depending on the person counting the cells. In addition, brightfield cell counting only provides a rough estimate of cell number, as the accuracy can be affected by the size, shape, and staining intensity of the cells.

Despite these limitations, brightfield cell counting is still widely used, particularly in cases where a rough estimate of cell number is sufficient, or when more advanced methods, such as flow cytometry, are not available.