Donno who made them, probably some guy in china, but they are everywhere. They are tiny multicolored pellets that you can find at railway stations. Some jelly like material that absorbs water. The cheap ones you get for something like five bucks, some shops offer high quality versions for a hundred bucks and upwards. No practical use, except for use with potted plants without having to use mud. I just clicked a few snaps of them - they are very brittle to handle, mind. The high quality ones can be thrown about a bit, and have a better coloring. The ones that look dark in the following photos are actually transparent.