a ceramic or metal container in which metals or other substances may be melted or subjected to very high temperatures.
"the crucible tipped and the mold filled with liquid metal"
a situation of severe trial, or in which different elements interact, leading to the creation of something new.
"their relationship was forged in the crucible of war"
When you put a popcorn kernel in a microwave, the microwave heats up the water. The water then evaporates, and the air wants to escape. There will be so much pressure that the skin/shell of the kernel will break, exposing the corn.
Could you show the characteristics?