Colored Scanning Electron Micrograph (SEM) of nylon hooks and loopsin Velcro material. Used as a common fastener on clothes and shoes,Velcro is a nylon material formed into two different structures: one a nail-head-like surface, and the other a smooth surface made up of a seriesof loops. The loops are loosely woven strands among an otherwisetight weave. When the two surfaces are brought together they form astrong bond, but can still be pulled apart. Magnification: 50 X.