In the interdisciplinary area of Web Science the Web is not only studied as a technological infrastructure but it is used as a telescope to study society at large. Research questions from fields such as sociology or psychology which were traditionally answered in small, timeconsuming studies are more and more answered by observing and mining online behavior of thousands or even millions of users. In this course we will look at current research in this area and learn about the data sets, the tools and the techniques used. As example applications we will see how this type of research can be applied to (i) study the spread of a influenza epidemics, to (ii) identify political issues and assign a leaning to them and to (iii) study the development of children and how it is linked to demographic factors. The course will feature a small, informal competition to come up with concrete project proposals addressing any odd, creative or simply funny research question pertaining to offline human behavior using publicly accessible data on the Web. The common thread throughout the course will be the question how findings from the online world can be linked to and verified against findings in the offline world.