Unless it is a tender plant it really should be kept cool. I believe where lots of peeps go wrong is they keep these little trees inside their homes, trying to keep them evergreen, when these are just tiny deciduous trees, well, unless they are little evergreen trees, but even so, they are mostly hardy and should be kept outside, in a sheltered spot. I have stacks of books on bonsai-ing and it is quite an amazing art. I would say go to the library and get a good book on it, if you are serious about doing it.