At the largest gathering of world leaders ever held in Washington, D.C., representatives from 47 countries met to discuss methods for controlling nuclear material. Top issues included how to keep that material from falling into the hands of terrorists and how to address Iran's nuclear weapon program.

While Iran has long insisted that its nuclear programs are for peaceful energy generation, the Obama administration has pushed for tough sanctions to keep it from building nuclear weapons, something that key players, notably China, have resisted.

It has also long been believed that Israel has nuclear weapons, although Israeli officials maintain a policy of ambiguity. Israel's president sent a deputy to the conference in his place amid tensions surrounding his country's weapons arsenal.

President Obama also called on other nations to slash their nuclear arsenals, just a week after he signed an agreement with

"There is no obstacle ahead of our scientists when it comes to nuclear science." - Mahmoud Ahmadinejad, Iranian president

"So, you will have two states, one on the west wing of the Arab world, the other on the east, Iran, Israel. And you have a large community of Arab states that would feel threatened of the presence of two nuclear states." - Egyptian Foreign Minister Ahmed Aboul Gheit

"Terrorists are definitely interested in acquiring either weapons or material." - Sharon Squassoni, proliferation prevention program director, Center for Strategic and International Studies

1. What is nuclear energy? What applications does it have?

2. Which countries have disclosed that they have nuclear weapons, and which countries have the most?

3. When is the only time a nuclear bomb has been used in warfare, and where did that incident occur?

1. Do you think President Obama's initiative to control nuclear materials will succeed? Why / why not?

2. What are today's main fears and issues surrounding nuclear materials? Why does President Obama want to control them?

3. If you were President Obama, how would you handle nuclear negotiations? Would you hold a big conference or several smaller meetings? Why?