Sigma-Aldrich was created in 1975 by the merger of Sigma Chemical Company and Aldrich Chemical Company. It grew through various acquisitions until it had over 9,600 employees and was listed on the Fortune 1000. The company is headquartered in St. Louis and has operations in approximately 40 countries.
In 2015, the multinational chemical conglomerate Merck Group acquired Sigma-Aldrich for $17 billion. The company is currently a part of Merck's life science business and in combination with Merck's earlier acquired Millipore, operates as MilliporeSigma. It is headquartered in Burlington, Massachusetts, United States.
Sigma Chemical Company of St. Louis and Aldrich Chemical Company of Milwaukee were both American specialty chemical companies when they merged in August 1975. The company grew throughout the 1980s and 1990s, with significant expansion in facilities, acquisitions and diversification into new market sectors.
1935 – Midwest Consultants was founded in St Louis by brothers Aaron and Bernard Fischer, who hired chemical engineer Daniel Broida.
1946 – Sigma was formed from Midwest Consultants and manufactured just adenosine triphosphate. They were the first to manufacture pure ATP.
2014 – Merck KGaA announced that it would purchase Sigma-Aldrich for approx. $17 billion (€13.1 billion).
November 3, 2014 – Sigma-Aldrich filed a definitive proxy statement with the U.S. Securities and Exchange Commission to hold a special investors meeting regarding approval for the sale to Merck KGaA.
1978 – Makor Chemicals
1984 – Pathfinder
1986 – Bio Yeda, Bristol Organics
1989 – Fluka Chemie AG (Swiss company founded in the 1950s) purchased for $39 million.
1993 – Supelco, Inc. acquired to enter the chromatography market
1994 – LabKemi AB
1997 – Research Biochemicals International, Riedel-de-Haen, Techcares Systems, Carbolabs, YA Kemia
1998 – Genosys
2000 – First Medical Inc., Amelung GmbH, ARK Scientific
2001 – ISOTEC (produces stable isotopes used in basic research and medical diagnostics)
2004 – Ultrafine (a supplier of contract manufacturing services for drug development), Tetrionics (a producer of high potency and cytotoxic active pharmaceutical ingredients)
2005 – JRH Biosciences, an industrial supplier of cell culture products for the pharmaceutical and biotechnology industries; Proligo Group, a global supplier of genomics research tools
2007 – Epichem acquired to expand capabilities in materials sciences and semiconductor markets; Molecular Medicine BioServices acquired to provide large-scale viral manufacturing capabilities; announced alliance with Sangamo BioSciences to develop zinc finger-based laboratory research reagents
2012 – Research Organics Inc., BioReliance (a toxicology and veterinary diagnostics company); BioReliance had previously been acquired by Invitrogen and subsequently sold to Avista Capital Partners.
Sigma-Aldrich Fine Chemicals (SAFC) is the fine chemical supply branch of Sigma-Aldrich specializing in raw materials for cell culture products; customized services for raw materials, manufacturing of active pharmaceutical ingredients.
Sigma Life Science provides products such as custom DNA/RNAoligos; custom DNA and LNA probes; siRNA; isotopically-labelled peptides and peptide libraries.
Sigma Advanced Genetic Engineering (SAGE) Labs is a division within Sigma-Aldrich that specializes in genetic manipulation of in vivo systems for special research and development applications. It was formed in 2008 to investigate zinc finger nuclease technology and its application for disease research models. Located in St. Louis, Missouri, SAGE Labs have developed knockout rats for the study of human diseases and disorders (such as autism), which are sold for up to US$95,000. SAGE also announced its first successful effort in creating a "knockout rabbit". Its facilities include a specific pathogen free, biosecure vivarium as well as research and development labs.
Carbolabs produces research quantities of chemicals produced by phosgenation reactions. The company was acquired in 1998.
BioReliance provides testing and manufacturing services to pharmaceutical and biopharmaceutical companies that span the product cycle from early pre-clinical development to licensed production.
The company was acquired by Sigma Aldrich in January 2012.
Matthias Heinzel became CEO of the Life Science business of Merck KGaA, Darmstadt, Germany in April 2021 following Udit Batra's departure from the company. 
^"Sigma-Aldrich Corporation Announces Filing Of Definitive Proxy Statement And Date Of Special Meeting Of Stockholders". Acquire Media. Archived from the original on December 28, 2014. Retrieved 3 November 2014.
^"Sigma-Aldrich Corp acquires Isotec Inc from Taiyo Nippon Sanso Corp".