Because of hand-wavy explanations, people sometimes get confused about why time-dilation appears to work differently than length contraction, in that time dilation has a permanent effect (one twin is now older than the other) but length contraction doesn’t (when the twins are back together, they are the same height again (barring effects of aging).
It took me a few minutes to realize what was wrong with that apparent discrepancy:
When the twins are back together both are, at that moment, the same height and aging at the same rate; however, the accumulated time that has gone by for them, and the accumulated distance they have traveled away from each other and have traveled together again are both asymmetric - the traveling twin has aged less and traveled less far, because he’s the one who has switched reference frames by changing his velocity.
@Chronos: is that right?