Spin labels are specialized molecules used in scientific research to study the properties of other molecules. They contain unpaired electrons, which create a magnetic moment, allowing researchers to track and analyze the behavior of the labeled molecules using techniques like Electron Spin Resonance (ESR) or Nuclear Magnetic Resonance (NMR). These labels can be attached to specific sites on a molecule, providing insights into its structure, dynamics, and interactions. By observing how the spin labels respond to their environment, scientists can gain valuable information about molecular processes in fields such as biochemistry and materials science.