Bright field microscopy is the simplest form of optical microscopy techniques. The sample is illuminated from below and observed from above with the attenuation of the transmitted light by the sample causing darker areas. It's the simplest technique and thus quite popular.

Chemotaxis BF10

This assay is optimized for bright field images of moving cells such as T-Cells. Choose this version of chemotaxis assay if your image and cells have similar characteristics as the image below.