Lesson of choosing a topic!

To choose a topic for a 15 page document may be easy: There are so many interesting things in this world to learn and write about. Or it may be difficult: It should be criticial, feasible within reasonable time, not to complex, but even though it should give the opportunity to "discover something".
Getting pratical - what I realized today: Better choose a topic that seems simple in advance because you can be sure that there is something tricky or complicated behind! Knowing before starting that the topic is huge and complex is underestimating the diverse and related mecanisms at the basis!

Therefore, I will be careful in choosing the topic of the next paper I should start writing before X-mas!