Over the course of its first 100 years, the National Institute of Standards and Technology (NIST) has made numerous contributions to advancing the science and practice of analytical chemistry. Contributions to fundamental constants and reference data, such as determination of the Faraday, Avagadro's number, and atomic masses, began at almost the beginning of the new institution when it was formed in 1901. Instrumentation development, improvement, and reproducible methods for its use have also been an important part of the NIST effort. This paper will describe what may be the organization's most important and certainly its most unique contribution; namely, certified reference materials. Ultimately these certified reference materials would become known at NIST as standard reference materials (SRMs). It is a contribution that now has been mirrored around the world with reference materials being certified in at least 25 countries and routinely applied in more than twice that number. The result has been more accurate analyses of materials that impact our safety, health, and well-being.