In silico study of functional transition metal nanoclusters refers to the investigation of the structural, electronic, optical, and catalytic properties of transition metal nanoclusters using molecular modeling techniques, often denoted as Computational Chemistry. Great progress has been made in Computational Chemistry towards its application as a practical research tool for all areas of Chemistry and Biochemistry since the early 20^th century. With breakthroughs in developing practical theories to deal with various Chemistry problems, coupled with the rapid development of faster and more powerful computers, software was developed and employed to study various properties of materials. The first milestone in the history of Computational Chemistry was marked by the appearance of commercial software, which allowed researchers to perform in silico studies of primitive problems, such as geometry optimization. The most widely used commercial software include Gaussian and Materials Studio. The climax of this stage of Computational Chemistry was the awarding of the 1998 Nobel Prize in Chemistry to Walter Kohn and John A. Pople for their contributions to electronic structure calculations; the development of the Density Functional Theory by Walter Kohn and computational methods in Quantum Chemistry by John A. Pople.