When creating a post and uploading an image, I need an additional thumbnail to be created from the uploaded image, in addition to the what is created automatically by WordPress. I am fairly new to WP but have created a custom theme and one plugin, so I have some knowledge. I'm guessing I need to create some sort of hook? to grab the image info when uploading it into a post, but I don't know where to start and haven't worked with hooks before. Any help would be appreciated.