Early Wednesday morning, North Korea claimed it successfully tested a "miniaturized" hydrogen bomb.
Global geological agencies registered a 5.1 magnitude earthquake at the reported testing site, but the secretive nation's claims have yet to be verified. Both the U.S. and South Korea have said the nuclear test "doesn't appear to be hydrogen-based," based the intensity of that tremor.
"Only a few countries, including the U.S. and Russia, have conducted hydrogen bomb tests, and the size of the detonations reached 20 to 50 megatons," a South Korean military official said.
North Korea's test on Wednesday measured 6 kilotons, which is far from the power a true H-bomb would release.
A hydrogen bomb would be a considerable advance in technology from the three earlier plutonium-based bombs that North Korea tested in 2006, 2009 and 2013. Hydrogen bombs are more difficult to make and are usually more powerful than atomic bombs.
Fusion is the main principle behind the hydrogen bomb, which can be hundreds of times more powerful than atomic bombs that use fission. In a hydrogen bomb, radiation from a nuclear fission explosion sets off a fusion reaction responsible for a powerful blast and radioactivity.
To put into perspective the power of a hydrogen bomb, we looked at the size of other explosions.
Tsar Bomba
The best historical example we can drawn from is Russia's "Tsar Bomba" hydrogen bomb test in October 1961. It had a power of 50,000 tons of TNT -- producing about 1,500 times the combined energy of both bombs that the U.S. released over Hiroshima and Nagasaki.
When it detonated over a test site in Russia, it produced a 64 kilometer-high mushroom cloud -- about seven times the height of Mount Everest. All the buildings in the village around a 55-kilometer radius were destroyed, and it's estimated that the heat from the explosion could have caused third-degree burns on people who were as far as 100 kilometers away.
Hiroshima and Nagasaki
In 1945, the U.S. dropped two atomic bombs over the Japanese cities of Hiroshima and Nagasaki. The first bomb over Hiroshima was uranium-based and carried a power of 16,000 tons of TNT.
It destroyed about 90 percent of Hiroshima, Japan's seventh-largest city. It's estimated that 45,000 people died on the first day, with another 19,000 dying over the next four months due to radiation poisoning.
The second bomb over Nagasaki three days later was plutonium-based -- similar to the ones used in North Korea's three tests. This one, nicknamed "Fat Man," packed 21,000 tons of explosive charge, but the death count was lower over the less populated area.
Tianjin explosion
Though it wasn't a bomb, last year's explosion at a Chinese chemical factory packed a force of 21 tons of TNT -- just a fraction of a hydrogen bomb's force.
Still, the shockwaves from this explosion damaged buildings in a 5-kilometer radius, and 165 people were killed. Windows and doors were blown in 17,000 apartments around the area.