Stop Motion Animation is created though the process of taking a series of pictures of a inanimate object to create the illusion of it moving, the more pictures will make it a smoother animation. Usually they use Clay or a Doll since both are able to be moved into many different positions, however this isn't always required as sometime a object like a pen can be used for a Animation.
There are many people who influenced Stop Motion Animation in it's Early Years like...
Joseph Plateau
William Horner
Emile Reynaud
Edward Muybridge
Edison
Lumiere Brothers
George Pal
Willias O'Brien
Ray Harryhausen
Jan Svankmajer