Recently, Samsung’s Galaxy Note 7 has run into some battery issues. According to a small population of customers, their phone battery simply overheated and exploded, causing a full recall of the product. Samsung tells the press that it’s because the battery was manufactured incorrectly–but the Galaxy’s battery isn’t the first to explode in the history of cell phones. What causes such modern technology to simply catch fire? And why do we carry that around in our pockets? Read on for a quick run-down of why batteries explode in the first place.