The world’s biggest climate case begins at The Hague in the Netherlands today. Oral arguments will be heard by the International Court of Justice (ICJ), which will consider what obligations United Nations member states have under international law to protect the planet from greenhouse gas emissions for future generations.

The International Court of Justice, the United Nations’ highest judicial body, is beginning landmark hearings on global warming. Here’s a guide.

Officials from almost 100 countries are at the International Court of Justice in the Netherlands, asking the court to issue an opinion on the responsibility of certain nations to protect the planet from climate change.