What is a hydrogen bomb and can North Korea deliver one?

CNN 2 hours 35 minutes ago 

What is a hydrogen bomb?

Hydrogen bombs, or H-bombs use fusion, the same process that powers the sun.

In a hydrogen (thermonuclear) bomb, "heavy" isotopes of hydrogen are forced together to release a much bigger punch -- hundreds or even thousands of times more powerful than the only nuclear weapons that have been used in warfare.

Atomic bombs use a process called fission. They split plutonium and/or uranium into smaller atoms in a chain reaction that releases massive amounts of energy.

Plutonium bombs tend to involve fairly large devices. Early nuclear weapons, such as the "Fat Man" device dropped on Nagasaki in 1945 -- which weighed around 4,700 kilograms and was a meter and a half in diameter -- were "much too large to place on a ballistic missile," according to weapons expert Jeffrey Lewis.

Miniaturizing any type of nuclear bomb so it can fit on top of an ICBM involves delicate balance between making the device smaller and not sacrificing eventual payload, which requires a lot of testing to ensure the smaller warhead is still capable of producing a devastating explosion.