The book explains rules and concepts of the quality. It also explains how to apply all the quality requirements so as to facilitate obtaining ISO certificates. The book shows different specific definitions to facilitate understanding the quality manual. It also shows names, types and requirements of the different ISO certificates. It explains the difference between the certificates related to the technical and the documentation systems. The book represents one of the most important books which deal with the modern topics of how quality applications and requirements in the laboratories. It also explains ways of calculations of uncertainty values and how to use the calibration certificates of the tools and certified reference materials in the uncertainty calculation. The authors in this manuscript explain concept of quality assessment and role of the assessor in the accreditation process. They wanted to present their experiences in the labs to simplify how to adopt different tests. They also explain the difference between inter-laboratory comparison and proficiency test and they showed how to rehabilitate laboratories even play a role proficiency test provider.