Panelizer: displaying node reference field I have an "Event" content type with a node reference field of type "Host".

"Host" content type has an "Affiliation" field.

I would like to display the event details though Panelizer, so that it would show not only the host name, but also their affiliation. How can I access a node reference field through panelizer?

My guess is that it should be done though the "Existing Node" option, but I might be wrong.
You'll have to create a custom formatter where you can control the output of the node reference. To create a custom formatter follow this tutorial: http://www.metaltoad.com/blog/drupal-7-tutorial-creating-custom-formatters

After that in panels when you add the node reference you can choose the custom formatter you've created: