First Velcro was made out of cotton by George De Mestral, although this cotton wasn't as strong as De Mestral had thought it to be. Today Velcro is made of various materials ranging from Nylon and pollyester to stainless steel and Synthetic fibers! The EXTREME Velcro (stainless steel and synthetic fibers) can withstand up to 800º F. without giving away!
Originally a multifilament yarn was weaved from velvet or cotton terry cloth to create a surface of hooped threads. A similar second multifilament yarn was created but the hoops were cut to create hooks. When the two fabrics contact with each other the hooks become entangled with the hoops. The same concept is used with other materials such as Nylon.