This may be drifting off topic just a bit, but this stuff is cool . . .
Some of the fun stuff are things you can see with light microscopy. One of the projects I worked on used isolated mouse cardiomyocytes (heart muscle cell). By applying electrical currents you can cause the cells to contract, and you can measure the contractions using the distance between the light and dark bands in the cardiomyocyte. The light and dark bands are alternating bands of myosin and actin, so you can see differences in protein using light microscope at about 200-400x magnification.
You can also get a fluorescent dye into the cells that fluoresce when they bind to calcium. Internally stored calcium is the signalling molecule that causes contractions, and you can measure the release and uptake of calcium over a few hundred milliseconds by measuring fluorescence hundreds or thousands of times a second. This is the graph that you get:
You get a spike of calcium that triggers the contraction, and then uptake of the Ca++ by SERCA2 back into the endoplasmic reticulum. This all happens in less than half a second.
This is somewhat similar to the G-protein pathway for neuropeptides, but it is a lot slower, obviously.