Those white crystals are called “dregs” and are solids leftover from the winemaking process. Dregs are sediment sometimes found in a bottle or glass of wine made of yeast cells, as well as leftover grape solids tartrates or tartaric acid crystals. These “lees” are the yeast grape tartaric acid sediment.
In fact, some wines are intentionally aged in contact with the lees “sur lie” to enhance flavor in adding complexity to white wines.
But a winemaker can also choose to “rack” the wine, meaning they separate the wine from the sediment. But if you find sediment—or dregs—in your glass, chances are it’s on purpose.