Good plan, Ax. For best photographs, try getting the light from the window behind you. Or shoot at night. Shooting through glass at roots and soil is tricky, I suspect. Try placing the camera on a tripod or couple books for support and use a short time exposure--flash may produce glare and reflections. Cover up the flash if necessary.
This could be interesting. Perhaps we can add water and shake up a jar of our local soil in a jar and let it settle. In theory, it should settle out in distinct layers, coarse particles, medium, fine and eventually tiny colloidal clay particles. What is the percent of each in your town? Naturally it probably varies.
At present...I have a bit of a snow situation. And glass jars are getting hard to find.
Most of my weed experiments are growing in purchased potting soil. I am raising tomato plants for a future weed control test, (4 inches tall). Suggestions? I only have 4 weed products to test at the moment. Various combinations could be tested. Or perhaps humidity effects.