I am a theoretical physicist by training although my thesis was actually on an experimental subject. See also the Mathematics Genealogy Project. For the last 30 years or so I work on industrial research where the common theme is thermodynamics of complex mixtures.
Some years ago I started to become interested in my ancestry, probably triggered by rumours in the family that we might be related to Rembrandt: my grandmother has the same surname and is from about the same area. Early 2013 I joined Geni, and I now seriously doubt if there is any link to Rembrandt, at least I haven't found it yet. But I made many other surprising and interesting discoveries, and became really addicted to genealogical research!