As challenges with security is increasing by the day ranging from evasion of privacy (for whatever cause) to stealing of confidential documents within and outside an organization, the need for effective and efficient security solution cannot be over-emphasis. Security based on gadgets like swipe card, keys and so on is fast becoming history due to the loop holes that has been explored as it can be misplaced, stolen and damage. Biometric offers a better solution, having a person physiological or behavioural trait to grant access rather than tokens. This book offers a detailed review literature of biometric technologies, approaches to multi-biometrics with emphasis on multi-instance biometrics. Matching at various levels are also discuss after which a robust architecture was designed and implemented taking security and flexibility of use as a priority.