Group IV metal Pb on Group IV semiconductor Si(111) substrate has been shown to be a very unique system in terms of epitaxy growth, in which various nanostructures such as islands with magic height and atomically flat films of novel properties have been reported.@footnote 1,2@ By controlling the Pb coverage and deposition conditions, we have achieved identical nanocluster array,@footnote 3@ nanowire array@footnote 4@ and ultra-thin films with atomic-scale uniformity.@footnote 5-7@ Our scanning tunneling microscopy and angle-resolved photoemission study reveals that quantum size effect (QSE) plays a crucial role in the formation of nanowires and thin films. In this talk, I will discuss how the QSE in this system modulates the density of states near the Fermi level and regulates the growth, and the correlation between electronic structure modulation and oscillating superconductivity transition temperature,@footnote 5@ surface stability,@footnote 6,7@ work function and chemical reactivity.@footnote 8@ @FootnoteText@ *In collaboration with Qikun Xue, Xucun Ma, Yan-Feng Zhang, Yang Guo, S. C. Li, S.B. Zhang, E. G. Wang, Q. Niu, Z. Q. Qiu and Zhong-Xian Zhao. Supported by the Natural Science Foundation of China and Ministry of Science and Technology of China.@footnote 1@ M. Hupalo and M. C. Tringides, Phys. Rev. B65 (2002) 115406@footnote 2@ M. H. Upton et al., Phys. Rev. Lett. 93 (2004) 026802@footnote 3@ S. C. Li et al., Phys Rev. Lett. 93 (2004) 116103@footnote 4@ L. L. Wang et al., submitted to Appl. Phys. Lett.@footnote 5@ Y. Guo et al., Science 306 (2004) 1915@footnote 6@ Y. F. Zhang et al., Phys Rev. Lett. 95 (2005) 096802@footnote 7@ Y. F. Zhang et al., Surf. Sci. 596 (2005) L331@footnote 8@ X. C. Ma et al., (unpublished).