Lithium-ion batteries power a ton of devices we use in our day-to-day lives – smartphones, tablets, laptops and more. And ever since they began showing up in all of our mobile devices, we’ve known that these types of batteries can be extremely dangerous. So, in hopes to find out exactly what makes these lithium-ion batteries tick, a group of researchers at University College London have been using 3D and thermal imaging to find out what happens before, during and after batteries overheat.

Taking a look at the video below, the researchers heated a pair of batteries to 482 degrees Fahrenheit (250 degrees Celsius), taking a close look at what happens at all points during the overheating process. One of the batteries reached its tipping point at this temperature, all thanks to a term called “thermal runaway”. One researcher explains:

Thermal runaway means that at a critical temperature, the materials inside these batteries start to break down. And when heat cannot escape as fast as it’s being generated, this is a “runaway” reaction that cannot be stopped.

It should be noted that thermal runaway only took place in the battery that didn’t have any internal support. So the battery that had this feature was heated all the way up to 1,832 degrees Fahrenheit (1,000 degrees Celsius). At this temperature, the copper internals began melting away, thus causing thermal runaway to eventually take place.

Obviously lithium-ion batteries won’t even come close to reaching these kinds of temperatures the way we use them today, but these are the kinds of tests that need to take place before we begin using them in more demanding and larger devices.