I know, it's fantastic. They are most probably professionals, or super talented artists. I started off with just basic anime drawings, and then I started to get more clever by adding expressions, different poses etc. Personally, the most hardest thing I can basically draw is myself, which might sound pretty stupid but it's true. I just simply can't draw myself for some odd reason. Using my observation skills, I might be able to draw myself by taking a picture and then sketch it, but there would be no other way.
That is what I'm pretty worried about if I wanna be an artist one day....