Since different kinds of economics thoughts have been explored, few have been as peculiar as Old Institutional Economics (OIE) and New Institutional Economics (NIE). It is curious that almost every stream criticizing mainstream economics has a left wing. OIE, not a big fan of this, criticizes neoclassical economics/mainstream economics, given it arose in the US. OIE had no sense to left wing, on the contrary, it created an effect criticizing neoclassical economics in its core. Unlike OIE, NIE has many common points with neoclassical economics. NIE has several new aspects different from neoclassical economics, as it has chosen a completely different path than OIE. In this chapter, authors scrutinize circumstances that led to OIE, and what separated OIE and NIE. A brief, successively historical aspect is also provided.