Note that slower crystallization produces larger and more irregular crystals.
Crystallization is a natural phenomenon which does not spoil the honey. In most cases, the crystallization process can be reversed by gently heating the honey to "melt" the crystals.
How to de-crystallize honey.
Honey that has started to crystallize, characterized by glucose crystals forming on the bottom of the container, can be easily melted. Simply put the honey container (with the lid on) into a warm water bath on the stove at approximately 45°C for a couple of hours, or as necessary. Stirring the honey occasionally will speed up the process.