A problem I have had is that it took me a very long time to find out on which topic I would focus my career. I have worked on Europa, Titan, asteroids, laboratory work, mission design, Mars, astrobiology, and material physics. However, I would not claim that I am an astrobiologist or a mission designer, or that I qualify to be part of a mission to Mars. That is the problem of being interested in many topics and getting the opportunity to work on all of them! I am not saying that it is necessarily a bad thing to have broad-based expertise, but it clearly took me a while to obtain enough results in a particular area for that research to become marketable, i.e., to obtain funding in order to be able to carry out that research to the next level.