Metallic glasses (MGs) provide ideal material platforms to study crystallization due to their simple metallic bonds and slow crystallization kinetics. But even for MGs, a direct observation of the crystallization process has been challenging, partly due to limitations in fabricating samples appropriate for characterization methods. We have recently demonstrated fabrication of metallic glass nanorods via thermoplastic forming, enabling us to directly observe crystallization using a transmission electron microscope (TEM). Here, we investigate crystallization of MG forming liquids by in-situ heating size-controlled MG nanorods down to ~5 nm inside a TEM. We show that the MG nanorod diameter affects the crystallization kinetics strongly. With decreasing nanorod diameters, crystallization temperature decreases initially, exhibits a minimum at ~ 30 nm, and then rapidly increases with decreasing size. In this talk, I will discuss this unusual crystallization kinetics. Factors are experimentally verified by slowed grain growth and scatter in crystallization temperature with decreasing diameters.