What's round and green and shiny all over? No, this isn't a set up for a punny joke — it's describing the world's largest single-celled organism: bubble algae. It's known as a sea pearl or a sailor's eyeball, per All At Sea magazine.
And bubble algae is the prettiest kind you'll ever see.
All At Sea reported that the marble-like balls can be found in shades of green, silver, teal and black, depending on where they're at in the water column. And their cellulose, which makes up the cell's walls, is structured in a way that makes them super shiny.
Like trendy-crystal shiny.
But, more often you'll see their shine dulled a bit by white, fuzzy algae hitching a ride on its smooth surface.
Still pretty, though.
According to Smithsonian, the balls can grow up to 2 inches.
And can we just reiterate?
They're each just ONE cell.
For comparison, another Smithsonian article reports that humans are made up of 37.2 trillion cells. Bubble algae has one, and it's a huge cell.
Could you imagine if we had 2-inch cells floating around inside and still had to fit 37.2 trillion? Impossible.
It makes sense then that bubble algae's scientific name, Valonia ventricosa, is Latin for "swollen, especially on one side," per Algae Base.
The fact that it's made up of just one large cell has made it a prime study object for scientists. Usually the cells they interact with are microscopic.
Valonia ventricosa gives researchers a chance to see how cells react not under a microscope.
Even though this algae is pretty spectacular, Smithsonian reported that it can be considered a pest to some.
There are actually quite a lot of videos online about how to get rid of bubble algae in fish tanks. It can take over if the conditions are right and cover everything.
No one wants their fish tank to look like the one in "Finding Nemo."
In any case, these underwater marbles remain both scientific marvels and pretty to look at.