Brainiacs mind's expand to increase their capacity to think, learn, and comprehend better. Add +2 Intelligence to inflate your knowledge and get the galaxy brain that's expected of you. Don't forget that sometimes knowledge intangible and to help with the lessons that are more philosophical, add +1 Wisdom. Your smarticle particles support all mental ventures. 

Depending on the humanoid that the Brainiac is based on, the lifespan can vary greatly. As a general guideline, they tend to live 20 years shorter than their race usually does. Although, as Brainiacs go, they can find a way to extend their lives if they wish.

Brainiacs tend toward True Neutrality. Life is a process and things happen as they will happen. Life and Death are just parts of the cycle. Right and wrong are subjective to those who judge. 

Brainiacs stand at the height of their base race. I will say that enlargened brain adds a foot to the height. I mean what do you expect? You are big brained. Let it show.

Your base walking speed is 30 feet. 

You know Common and can choose two extra languages. You know how to read, write, and speak each language.

You gain advantage on all Intelligence ability checks.

Brainiacs have the ability to interact just slightly with other brains. As an Action, you can send harmful shocks to other creatures with your brain. The creature must succeed on an Intelligence Saving Throw. The DC is 8 + Proficiency Modifier + Intelligence Modifier. On a failed save, the target takes 1d6 of Psychic damage.