Honey, especially raw honey, will often become solid over time. This is known as crystallization or granulated honey. Honey with high sugar content (greater then 70%) tends to crystallize the fastest.
Crystallized honey is totally safe to eat, and can easily be returned back to a liquid state.
Warm up some water in a pot or pan. The amount of water is dependent on how tall the glass honey jars are. You want the water to go about 1/2 or 2/3 of the way up the side of the jar.
Uncap the honey, and place in the pot. Note that the honey must be in a glass container. You want the water to be hot, but NOT boiling.
Stir occasionally to help loosen up the crystals. Make sure you don't get any water from the pot in the honey jars.
Soon it will be nice and runny.
When it is done, remove from the heat. The jars will be warm.
Tightly seal the jar before storing. The ideal storage temperature is between 64 and 75 degrees. Never store honey in a refrigerator.