The Thermo Fisher Scientific Inc. board of directors has approved the acquisition of electron microscopy developer FEI Co. of Hillsboro, Ore., with a purchase price of $4.2 billion. The transaction is expected to be complete by early 2017. Thermo Fisher cited FEI’s electron microscopy platform as an important addition, given the growing adoption of this technology for the study of protein structure. Thermo Fisher Scientific is a biotechnology development company. FEI designs and manufactures microscopy technology.