Fermentation is the magic bit of wine making - sprinkling fairy dust yeast on a bucket of fruit juice & the juice turns into wine.
As CJJ says, 'when the yeast is put into a sugary solution, it begins to multiply vigorously & in the complex chemical processes which ensue, the sugar is converted roughly half to alcohol ... & half to carbon dioxide...'
And just a day or so after adding the yeast, not only are there warm & yeasty smells coming from the bucket, but there's a constant shifting in the surface froth as bubbles burst & new ones break to the surface & listen closely & you can hear the fizzzzzzzzzzz of all that yeast furiously multiplying, feeding on the sugar & exuding alcohol & gas.
Actually, examining the process in that much detail makes it all sound rather mundane & more than a bit grubby.
We'll stick to the magic fairy dust, I think.