Many years ago, when I was a kid, I was pretty curious about the aliens, and thus read a lot of reports and programmes related to UFO and extraterrestrial creatures. At that time, I firmly believe in the existence of aliens. However, as time passes by, I got access to more and more papers and studies made by scientists who found there was no direct evidece proving the existence of aliens, I started to doubt the credibility of the videos and reports I have read when I was young. Until recently, after I watched some documentaries relative to the exploration of outer space, I realised the plants and stars we have already known are quite limited, and there are still a bigger universe for us to study. Therefore, only based on the current scientific data we have gathered so far can not give us the certain answer whether the aliens exists or not. We still need to find ways to access to more space of the universe to figure out the answer to this debatable topic. Moreover, the discovery of key elements to survive the life on some planets also indicate the possibility of the existence of some creatures in the universe apart from human beings.