when did it start for you?  

Simply?...
LEGOS, and the fact that if was building something and did not have all the right color pieces to complete the project it went "unrealized".
Also, the fact that every Sunday when I got a pack of Haribo Gummy Bears I would divide them all up by color before I ate them...

From Koen's description I...
From Koen's description I feel like I would like to be a designer that time 🙂 although it would definitely be much more tough job then nowadays.
I've recently finished my design studies and from time to time thoughts on design education come to my head :). Sometimes I feel a bit envious to those studying at well known elite schools just like RCA or Eidhoven, i feel like I never get those contacts and knowledge they have chance to get. On the other hand I kind of enjoyed atmosphere of my town and the fact I had lot of time to discuss various topics with my teacher (as there weren't so many students coming regularly to classes.) I probably wouldn't have chance to at those schools? However my knowledge about other schools is quite poor. I only know a bit about some in my country, and I've spent one term in Germany {but that school wasn't that famous). So if someone knows more about those schools, I would be happy to learn something :).
Anyway, to the topic of this thread: I came to design quite accidentally. Almost at the end of my grammar school I was quite confused not knowing what should I study further. Nothing looked just right to me 🙂 until I started to attend drawing lessons and found out this looks interesting to me. And then came my interest in design, although at the beginning of my studies I had really poor knowledge about what is design really about. {anyway big part of exams was about drawing, and I passed in only on second try). But now I'm really happy about how things turned out..