HA1 shows a cellular process (growth cone) of an axon called a lamellipodium. This is the flattened, leading-edge region of a motile cell. The distributions of the microtubules (green fluorescence) and actin filaments (red fluorescence) are an example of how cytoplasmic filaments provide structural support for cells and their processes. Both types of filaments are dynamic and actively change length (polymerize/depolymerize) and position as needed by the cell in response to external stimuli. In a light micrograph these filaments are not visible, but use of a certain wavelength of light allows one to see the fluorescent signal and the positions of the filaments. The Original images have arrows/pointers to help you focus on structures, organelles and cells that are the important points of the exercise. You can use these arrows, arrowheads and numbers to quiz yourselves as you review.