How to get large thumbnails from YouTube videos

YouTube thumbnail maximum resolution
You made a YouTube video, published it and now you want to share it with the video thumbnail. First time I came across this myself I found out that the default thumbnail for you video is very small. You go to your "Creator Studio" page on YouTube and save the thumbnail of your video. Right click and then "Save image as". This gives you an image of 120px wide and 90px height. Very small. So where are the larger images?