Newton-X development started in 2005 based on surface hopping codes developed by Granucci et al. The first paper describing Newton-X (version 0.13) was published in 2007. Seven years later, a second paper reported the new developments in the program, at that point, still in version 1.4. Since then, other eight years have passed, and Newton-X has branched into four stand-alone software packages (Figure ):