Here is the microscope that was used to take those pictures:
In case you're wondering, the greyscale image in the previous entry is a layer of human cells. The green image is the same field, looking at something called 'green fluorescent protein' (GFP). GFP comes from a jellyfish; it's a protein and it fluoresces green when you shine blue light on it.
Here's the experiment: I transfected some cells — that is I forced foreign DNA into them — with the gene that codes for GFP. The clever bit is that the GFP gene was joined to the gene that codes for the protein I'm working on. In some of the cells the gene fusion DNA made it to the nucleus and inserted into the genome — the cell's own DNA. Once there, the cellular machinery looked at it, and made an RNA copy of it (it was transcribed into messenger RNA). The messenger RNA came out of the nucleus and was seized upon by ribosomes, which read the code in the RNA and translated it into protein; specifically GFP fused with my protein. Because my protein has a 'nuclear localization sequence' the entire fusion was then shipped back into the nucleus and that is why the nucleus of these cells glow green.
The thing that never ceases to amaze me is that this kind of thing is going on all the time in (nearly) every cell in our bodies. All the time.
I got excited because some of these cells appear to be doing something quite interesting, but further study and some reading makes it look like it is really an artefact caused by the promoter that was used to drive the GFP-fusion expression. Bah.
