Fluorescence recovery after photobleaching (FRAP)

There are many different ways to examine what is happening inside a cell. Most approaches look at a snap shot of a what is happening at a given moment (like a microscope picture of a fixed cell or tissue) or the average of what is happening (like the overall levels of a protein or RNA in a cell). If you put many of these snap shot or average experiments together you can come up with a pretty good guess of what kinds of processes are occurring. But if you want to see what is happening as it is happening you have to use live cell imaging. For this you have your cells growing happily in a dish and you use a fancy microscope that maintains the cells' temperature and CO2 levels while taking pictures, so the cells keep growing happily. In the end you get a movie of whatever your cells were doing.
I have been doing lots of experiments with a special variety of live cell imaging called fluorescence recovery after photobleaching (FRAP). FRAP relies of having a a colorful signal attached to mobile molecules. If you use a powerful laser to bleach all of the color out of a particular area then you can watch how quickly the color returns and get a sense of the rates at which the processes you are interested in occur. For most things moving around the cell by diffusion the time to recovery is on the order of seconds. My stuff if uncooperative (it moves around by an actual transport system), so the time to half recovery is about 40 minutes on average. That means that it takes a very long time to collect the replicates of data that I need. So my friend the microscope and I have been getting awfully chummy and watching movies together. It works out well.