Dichroic: Literally means "two-color". In microscopy, it is taken to mean that an element of the system, usually a mirror, will reflect light of a (usually) shorter wavelength ("bluer light") and pass light of a longer wavelength ("redder light").

Epifluorescence:  A system where the stimulation and collection of fluorescence is done through one lens. This form of microscopy relies on a special mirror known as a "dichroic" to split the excitation beam from the emitted fluorescence.

Fluorescence:  When a substance absorbs short wavelength light and produces longer ("redder") wavelength light, it is said to be fluorescing. For example, if blue light shines on a fluorophore called FITC, green fluorescence is produced, as shown below.

Fluorophore: A substance that produces fluorescence when light of the appropriate wavelength shines on it. Fluorophores are typically attached to parts of cells, or molecules on or within the cells that are being studied.

These cells (neurons) are fluorescing green or red, depending on how they absorbed red and green fluorophores

Image Stack:  When a confocal microscope produces a set of images at different heights within a sample, the entire set of images is referred to as a stack.

Nomarski (DIC):  Method of transmitted light imaging that creates contrast in the image depending on the rate of refractive index change within the sample. Also sensitive to changes in polarization within the sample. "DIC" means differential interference contrast.