Rights: University of Waikato. All Rights Reserved. Published 29 February 2012 Download

Dr Rebecca Campbell (University of Otago) discusses the importance of fluorescent molecules in confocal laser scanning fluorescence microscopy (‘confocal microscopy’) of cells. She explains how green fluorescent protein (GFP) from jellyfish can be used to make specific neurons glow green.

Point of interest: Look out for the fluorescent jellyfish in this clip!

Jargon alert: Confocal microscopy is a specialised form of optical microscopy that makes it possible to take pictures of many thin slices in a sample without actually slicing the sample up. The individual slices can then be built up into a three-dimensional model.

Jargon alert: Green fluorescent protein (GFP) is the most widely used fluorescent protein in microscopy. When viewed using a confocal microscope, cells containing GFP glow bright green in the parts of the cell where GFP is found. Scientists use GFP and similar fluorescent proteins in many different ways – to label specific types of cell (as Rebecca does), to label individual structures within cells and to look at changes in living cells over time.


The confocal microscope requires fluorescence to be able to look at specific focal planes within a section of tissue. There are a whole range of different types of fluorescent molecules that can be excited at different wavelengths and emit at other wavelengths, so we can label multiple features within biological tissue.

Some of the important fluorescent molecules that we use include green fluorescent protein, which is also known as GFP, and green fluorescent protein was initially discovered in jellyfish. So if you shine a particular wavelength of light on this extracted protein, it emits a green colour. So we’ve been able to harness this protein and use it to generate transgenic mouse models. We’ve generated a mouse model that inserts this protein into the gene of GnRH, and so what that allows us to do is to turn on this GFP protein specifically in the GnRH neurons so that, when we take out a slice of the brain and we look at it under a specific wavelength of light, it turns on this green light bulb in all of these cells so that we can find them within the brain tissue and target them to be able to record their electrical activity or to pull out their intracellular contents or, like what we do, fill them with small molecular weight dyes so that we can appreciate their morphology

Invitrogen™, Life Technologies™
MBL/Tom Kleindinst