Smart but dangerous
Felting needles are simple but smart tools designed specifically for needle felting. Their cross section near their tips is triangular and they have a few tiny barbs on their edges. What are these barbs for? When you stick the needle into the wool, they hook on the fibers and push them deeper. This way you tangle fibers with each other and give a desired shape to the item you work on. It is like carving a piece of wood bit by bit.
If you would like to know how long it takes to make something this way and how the process looks like, you can read my description of the needle felting technique. But before you do so, take another look at felting needles in the pictures and just imagine, how careful one needs to be when working with them.