Humans

Humans (人間, Ningen) are a species native to their world they called Earth. Human technology is considered primitive compared to other intelligent species, such as Cybertronians. However, Humans and Cybertronians have many different things in common, like science, history, biology and team work.

"They're such undependable creatures. Inferior lifeforms."
 * —Starscream

Anatomy and Design
Humans are built similarly to Cybertronians only being organic rather than metallic in nature.

Relations with Cybertronians
The Autobots and Decepticons are divided on the subject of humans. The Autobots wish to protect humans while the Decepticons viewed them as insignificant pests and doesn't register them as anything more than "collateral damage". Arcee and Ratchet thought protecting humans would result in more tragedies like Cliffjumper's death at the hands of Starscream.

The majority of humans are unaware that Cybertronians exist on their own planet. The U.S. government is aware of both sides and is an ally to the Autobots, though the majority of humans are concerned or wary about trusting them. MECH, became aware of them after trying to secure the DNGS. Many other humans have caught Cybertronians on camera in robot and vehicle mode (mostly Bumblebee), but have been removed by using Cybertronian software and a humans computer expertise.

Negative Effects from Energon
Despite having existed on their planet for years, humans are even more vulnerable than Cybertronians to the effects of Energon. This would show that human nervous systems and energon do not mix well.