Dearest gentle listener: It’s our first birthday! To celebrate one year of our What in the World podcast, we asked you what burning questions you had — and we turned to the BBC’s global network of experts to get the answers. In this episode, you’ll hear…

Digital health editor Michelle Roberts on how vaccines train the body’s immune system.

Seoul correspondent Jean Mackenzie on what tourists in North Korea can actually do.

Correspondent Samira Hussain on how the electoral college decides the U.S. presidential election.

Climate and environment researcher Mark Poynting on the role of hydrogen in the green energy transition.

Plus Mora from the What in the World answers Alex’s question, “How do fringes happen?” We said no question was too stupid.

Instagram: @bbcwhatintheworld WhatsApp: +44 0330 12 33 22 6 Email: whatintheworld@bbc.co.uk Presenter: Hannah Gelbart Producers: Alex Rhodes and William Lee Adams Editor: Julia Ross-Roy