Do Aliens exist?

This is a pretty interesting question that do aliens exist or not?Since man entered into the field of space,he showed a very  keen interest in finding the existence of other living organisms and other forms of lives on the earth,other planets,space and in the whole universe.
One such organism is supposed to be hidden from human's eyes.This is an Alien which is a creature existing outside from the earth or somehow hidden from human's eyes.Even it may be possible that they live among us on the blue planet-the earth,but we are unable to find them.They do not want to interact with us,because they do not want to share their habitat,technologies,civilisations,traditions etc.Also the reason behind it may be that they are afraid of us.
There is no confirmation that either aliens exist or not,but some evidences have been found even before the development of science that reveal the existence of aliens.Some scientist believe even including Stephen Hawkins,one of the greatest cosmologist,that we should be careful of aliens because they may cause a huge destructions for us.