The second kind of sampler is the injection core, which looks and works just like a pushcore, except there’s a valve and tubing at the top through which the scientists can squirt various chemicals. They might inject a preservative like RNALater or formaldehyde, or a marker like CellTracker Green® (CTG), which only labels living cells. CTG gets into living cells, where enzymes called esterases clip off the end of the CTG, which then fluoresces green. It’s a way to find out if cells were alive when you found them. Sometimes dead cells can look like they’re alive, especially in a place like a brine basin where the high salt concentration essentially pickles the cells. But dead cells don’t have esterases, so no matter how good they look, if they are dead, they won’t clip CTG and they won’t glow green under fluorescent light.