In modern technology there is an increasing demand for miniaturization of functional building blocks. Therefore engineering of systems on a molecular level by ‘bottom up’ approaches is desirable in contrast to classical ‘top down’ approaches like UV-lithography in semiconductor industry. One promising way to realize the fabrication of functional structures from molecules is through self-assembly on well-defined surfaces. In order to control the arrangement of the corresponding molecular building blocks on the surface it is essential to characterize and understand the adsorbate- adsorbate as well as the adsorbate-substrate interactions which determine the assembly processes. In this regard scanning tunneling microscopy (STM) has proven to be a very suitable method to determine the adsorption behavior of large organic molecules on solid surfaces and partially also their intramolecular conformation.