I came across this program while doing some image work for a project in my Cellular Biology class at UW- La Crosse this week. It came in very handy for manipulating my images beyond what my Aperture program can do, like merging. It's free, so I figured maybe somebody would find it handy.
The program is called ImageJ it's a very small file, just google search ImageJ and you'll find the link for it. Here's what's capable of doing:
The red filaments are actin filaments, green are microtubules, and the DNA/nucleus of the fish cell is blue. The way you have to take these fluored images with a the microscopes, one fluoresces blue, one green and one red and you need to take pictures of them separately. This lil' program allowed me to composite them for a real view of how these cells look :-) Check it out!