Biometrics is the measurement of inherent physical characteristics. This method is as old as humanity itself. In the context of counter-terrorism, biometrics has now gained a new significance: it is intended to make our lives safer. At the same time, critical voices are being raised questioning the application of biometrics: Should individual freedom be sacrificed for the sake of collective security? Are we on the brink of becoming transparent citizens, or are we already living in an Orwellian surveillance state? Is data protection equivalent to terrorist protection? In short: Is the measurement of humans excessive? This book examines these questions against the backdrop of how biometric methods can aid in counter-terrorism, where their limits lie, and what consequences they have for our daily lives.