Transferring the wort (unfinished beer) from the fermenting tub to the priming tub. A slurry of yeast and hops stays in the fermenting tub. Now we add a little sugar (this is “priming” the yeast). The yeast that’s still dissolved in the wort, which had gone dormant after using up all the wort’s nutrients, wakes up and starts making alcohol and carbon dioxide again.