(Book Series: Advances in Sensors: Reviews, Vol. 6). This open access book contains 21 chapters written by 94 contributors-experts from universities and research centres, from 21 countries: Argentina, Austria, Brazil, China, Czech Republic, Denmark, Finland, France, Germany, India, Italy, Japan, Mexico, Poland, Romania, Russia, Slovenia, Switzerland, Thailand, UK and USA. This volume is devoted to various chemical sensors (sensors for various gases, nucleic acids, organic compounds, nanosensors, etc.) and biosensors. Like all volumes from this Book Series, the volume 6 has been also organized by topics of high interest. In order to offer a fast and easy reading of each topic, every chapter in this book is independent and self-contained.