A Year Ago I Put Saltwater in a Jar [video]
I live near a fresh-water lake in the middle of Europe, and decided to do this experiment with my kids a few years back .. we took a jar, scooped up some water, threw a couple small bits of algae in, and took it back to our kitchen, where we watched it daily for months.<p>It was extraordinary to see things growing right away .. the kids loved getting up and checking on 'the critters and the goop', as we called it.<p>Our patience was rewarded when I spotted a tiny hydra had attached itself to the side of the jar ..<p><a href="https://en.wikipedia.org/wiki/Hydra_(genus)" rel="nofollow">https://en.wikipedia.org/wiki/Hydra_(genus)</a><p>We watched it grow and grew, going from near-microscopic to the size of one of the kids finger nails, turning a deep and vibrant red as it aged.<p>There were lots of other things too, which we never got quite around to naming .. freshwater shrimps, a couple of tiny fish (which didn't survive a heat-wave also, alas) .. but eventually it became a murky mess, and we cleaned the jar out for other experiments.<p>This is a really neat way to teach kids about life, in my opinion.  The next time we do it, we'll rig up a USB microscope and have it pointed into the depths - I have a feeling that my kids are going to find operating the microscope far more intriguing than any video game.  Would be grand to discover there's a microscope out there that can be remotely moved .. we may have to cannibalise a 'light following flower robot' to rig up our own "Exploratorium"™ .. ;)