The most realistic alien species you can imagine

In your opinion what alien species would you believe was most likely to exist in reality? For me its probably a big ol jellyfish alien, with a body similar to that of our own species but with the head of a jellyfish and the tentacles leading down its back.<br><br>I think aliens with human like bodies is the most realistic option for me because all life on earth is built around cells. The cell is the building block of all life, its the most basic level that life is made out of, so the most realistic alien species you could imagine would probably be a alien made entirely out of cells, with cells working together to form its body, much like our own bodies.<br><br>So what do you guys think? What do you think aliens would look like in reality?