If you live in a fog-enshrouded, low-lying area, it's a good night for laser fun. Even my low-power red pointer shows a visible beam in the fog. You can see density differences in the fog by sweeping the beam of a green laser back-and-forth rapidly. Lower-density patches are darker, and there is structure to them. My daughter waved her laser horizontally, and I waved mine vertically with both fans intersecting in the middle. We got a good 3-D view of the fog density distribution in an enlarging cone with us at the apex. My daughter was surprised to see just how non-homogenous the fog layer really is. Much wispy, filamentary structure, very similar to astronomical nebulae. It reminded me of those computer-generated maps of cosmic structure, also typically a cone-shaped region diverging away from our viewpoint.