An IEEE Spectrum article summarizes recent developments in the electronic noses. The latest variety sensors to give machines a sense of smell are based on conducting polymers that produce electrical signals in response to certain chemicals. The human nose, which is not particularly capable, as noses go, can detect about 10,000 different chemicals, known as volatile organic compounds (VOCs). Often, a single unique scent is the combination of hundreds of different VOCs. Early electronic sensors could only detect single chemicals. The most recent polymer noses are printable organic semiconductors that can "differentiate between basic classes of odors, such as acids, alcohols, amines, and thiols" allowing them easily sniff out the difference between wine and vinegar. There are still some bugs to work out before this technology becomes commercially available. For more, see our older articles on the NASA ENose, the NIST optical nose, and the nanobiosensor nose.