Peptide aptamers are artificially created short peptide sequences that have specific recognition abilities. The technique to create peptide aptamers has been developed in biology field and many peptides that bind to various biomolecules including enzymes, receptors etc. have been isolated since 1990. Recently, this methodology has been applied to create artificial peptides that specifically bind to the surfaces of inorganic materials. Here I introduce our studies on peptide aptamers against titanium and carbon nanohorns, and discuss on the "specificity" that is required for bionanotechnology.