You can buy socks that have tiny nanoparticles of silver. The nanoparticles are a few hundred nanometers in size and made up of mostly silver atoms.  The silver prevents microbes from growing which is what makes your feet stink. Scientists have found that washing these socks releases some of these nanoparticles which might not be good for the environment. It also means that the socks might someday become stinky because there are no more nanoparticles to kill the microbes.