Brightfiled microscopy Brightfield Microscopy:  
   Standard transmission of light through the cell, which has very little contrast. A cell is 70% water, thus most of the cell is basically colorless and translucent, i.e., invisible to the eye.
Phase Contrast Microscopy Phase Contrast Microscopy:
Incident light [Io] is out of phase with transmitted light [I] and when the phases of the light are synchronized by an interference lens, a new image with good contrast is seen. 
Nomarski Microscopy Nomarski (phase-contrast) Microscopy:  
is also known as differential interference contrast microscopy. Synchronizing of the different phases of incident and transmitted light is done by a set of special condenser lens mounted below the stage of a microscope = greater contrast
Dark Field Microscopy Dark Field Microscopy:  
Here the illuminating rays of light are directed from the side so that only scattered light enters the microscope lenses, consequently the cell appears as an illuminated object against the view.