It's like a little pin (and it hurts too like a pin!). Now, as I want to hear your "ohhhhhhhhhh", here is a picture of the hook and the thread I use when I make my minis:
I wrote a new pattern of a full jointed (5 ways) sock monkey, with movable limbs and head (it is on sale in my Etsy shop). Here is a picture of the little guy:
The sock monkey is made with Finca cotton thread but I always say that if you use a smaller hook and thread you'll make a smaller guy, so here are the pieces of the same sock monkey made with the same pattern but with a 0.5mm hook and sewing thread:











