It's amazing how much life lifts in with just that bit of soil; I have a few jars from three years ago (that I leave mostly closed) which have shown multiple generations of woodlice, water snails, little mussels, spiders, water fleas, beetles, worms. Sometimes, the whole pot turns opaque green for a few days, and then a few days later it clears up and I find some new life in there I have never seen before.
Highly enjoyable to have on your desk or in the window sill!