Because of thermal shock, which is when cracking or breakage happens as a result of extremely hot objects (contraction) coming into contact with cold objects(expansion), causing molecules to expand, we like to see the pottery handled with this awareness as it will surely increase its longevity. This goes for ALL pottery, not only ours - which is one of the most durable clays. This means maybe waiting a minute before pouring bubbling, boiling liquid directly into a cold cup..(or putting the cream in first helps cool down the coffee, tea or water). Microwaving seems to be usually ok for mugs but NOT plates or bowls where you might have varying degrees of food temperatures heating at different rates. They ARE dishwasher safe! And of course food safe, meaning food will not leach out anything toxic such as lead in some earthen ware or other low fired pottery. We have had customers report using their mugs and plates daily for 25-30 years with little wear and tear and no breakage.