Scientist testifies about the events that led to the explosion at Chernobyl.

Workers at Chernobyl only have 90 seconds to clean off the graphite on top the roof in order to avoid the exposure to radiation.

Russian hospital deals with the aftermath of the Chernobyl explosion. Workers must figure out how to treat chemical burns.

Gorbachev meets with a panel of people to discuss the update on the clean up from the explosion at Chernobyl. After being briefed on the clean up efforts, Gorbachev must make tough decisions on the next step.

Leon Trotsky criticizes his opponents in one of the most quoted speeches as the Bolsheviks consolidate power over the Petrograd Soviet and the Russian Revolution in general while modern experts weigh in.