What if a scientist wanted to visualize and study one specific protein in a cell with a microscope? In a typical cell all of the proteins would appear dark. In order to visualize a protein, scientists must engineer a fluorescent protein. Imagine an individual standing in a dark room; this person cannot be seen to anyone else in the room. However when the individual turns on a flashlight everyone can identify where that person is. Scientists can do the same thing with proteins. Instead of a flashlight, scientists attach a fluorescent tag onto the protein. This is done by cloning. One of the most common fluorescent tags that is attached to proteins is called green fluorescent protein (GFP). GFP was originally found and isolated from a jellyfish. Similar to how fireflies can produce a light, this jellyfish produces a green light. In order to turn on the protein, it must be excited by light. With the use of a microscope the fluorescent protein will turn on, or fluoresce and the protein will appear green in colour. GFP can also be altered slightly to release a different colour of light, for example red fluorescent protein, RFP or blue fluorescent protein, BFP.