This book summarizes protocols and applications of recently developed or improved non-radioactive biotin-labeling techniques for proteins, glycoproteins and nucleic acids and will provide valuable help to researchers both in fundamental and in applied sciences. The first chapter of this volume compares the chemical properties of biotin-labeling compounds currently available and outlines their reaction principles. The following contributions provides a step-by-step protocol on how to prepare and successfully apply biotin-labeled probes for the analysis of complex biochemical and cellular systems. An extended troubleshooting section completes each of the protocols. In most cases these core protocols provide a guideline that encourages modifications according to the researchers' experimental designs. Combined with sensitive detection, these recently developed experimental procedures are powerful tools for many applications in areas ranging from protein biochemistry to molecular and cellular biology.