It's considered to be the most severe nuclear disaster of all time: On April 26, 1986, an explosion and fire at the Chernobyl nuclear plant in Ukraine released massive amounts of radiation into the atmosphere. The Soviet Union, which at the time had jurisdiction over Chernobyl, didn't publicize that the accident had happened until the first radiation plume set off alarms in Sweden.

Radioactive clouds spread in virtually every direction during the week after the meltdown at Chernobyl. Areas close to the plant - in Ukraine, Belarus and Russia - were heavily contaminated. Heightened levels of radiation were also measured across nearly all of Europe after the accident. The so-called 'exclusion zone' around Chernobyl remains off-limits to human habitation to this day.

Aside from the dozens of people who died as a direct result of the accident, thousands more were later struck with cancer. An increase in mutations and birth defects was also noted among children of people exposed to radiation, as seen in this photo from 1989. Animals in the region also suffered from infertility or birth defects after the disaster.

Rainfall in the months after the Chernobyl reactor meltdown washed nuclear fallout into the foodchain, affecting livestock and wild game across Europe. Of the nearly half a million wild boars hunted and slaughtered in Germany in 2010, more than 1,000 contained higher-than-allowed levels of radioactive contamination.

Although the exclusion zone was evacuated and badly-affected areas were dismantled and buried, severe effects of the nuclear disaster are expected to continue in the area for at least another hundred years. Some heavily-contaminated regions won't be completely free from radiation and safe for human habitation for another 20,000 years, studies show.

The concrete cap built over the nuclear plant right after the disaster has been showing signs of decay recently and needs to be replaced. A new steel containment shell is currently being built on-site with more than 2 billion euros (nearly $2.5 billion) of international funding. It will be slid into place over the old sarcophagus by 2016.

After humans left the Chernobyl area in 1986, wildlife moved back into the newly-available habitat. Although some plants have genetic mutations, biodiversity appears to have increased partially. Some scientists even think the radiation may be speeding up adaptation. The zone has become a type of involuntary park, with predators such as wolves and eagles, and reintroduced wild horses.

In March of this year, a study was published showing that trees in the nearby Red Forest - where trees turned a rusty color and died after the disaster - are decaying slower than normal. This is due to a lack of living microbes and organisms in the area. Due to this excess of dried wood, a catastrophic wildfire could result, which could destroy the forest completely.

Nearly 25 years after the Chernobyl disaster spread fear across Europe, an earthquake and tsunami triggered a meltdown at the nuclear plant in Fukushima, Japan in March 2011. Some countries have since reacted by shifting their focus away from nuclear power and towards renewable energy. Germany has pledged to close its nuclear reactors by 2022.

If the national renewable energy plan is maintained, the share of renewable energy could reach 13 percent by 2030. But foreign investors were somewhat scared off when the Ukrainian energy commission sharply reduced its feed-in tariff at the beginning of 2015. So although Ukraine has been working on renewable energy, its future seems uncertain.