plots revolves like this...
professor vaseegaran(Rajini) creates a human android robot which resembles him . He names it chitti . sana (Aishwarya) is professor vasi's girl friend. chitti knows all skills of defense , languages of world and he is very intelligent.. Vaseegaran prepares Chitti for an evaluation by the Artificial Intelligence Research and Development Institute (AIRD) ,which is headed by Dr. Bohra (vasi's professor) , he wanted to gift it to indian army ....Through following situations and incidents vasi understands that chitti need to understand human psyche, behaviour and emotions, and succeeds in doing so by installing a new hormone simulation module into the robot. But problem comes through when chitti falls for sana and Bohra's thoughts to use chitti in bad ways.. finally a situation araises when vasi destructs chitti and chitti being remade as destructor by Bohra , which makes chitti kill Bohra , kidnap sana and built up his own army which becomes a big danger to humans... finally it becomes a war between the creator and the creation .. finally things come under control after great affords by vasi .
In a final court hearing, the judge rules Capital punishment for Vaseegaran for the number of human tolls caused by the robot army. Chitti, explaining to the court that the law allows him to be treated as a valid evidence, explains that it was Dr. Bohra who caused Chitti's deviant behaviour. He shows the court, using his eyes as 3D projectors, the video footage of Dr. Bohra installing the red chip inside him. The court decides to drop all charges against Vaseegaran, while concluding that Chitti should be dismantled in order to avoid further mishaps of the same kind in future. The court also observes that a robot as advanced as Chitti is "unnecessary for contemporary human life".
Back at the lab, in the presence of government and police officials, an emotional Vaseegaran tells Chitti to dismantle itself. While taking off its parts one by one, Chitti apologizes to Sana and Vaseegaran for the problems it caused.
20 years later, in 2030, students in a science museum are escorted by a guide towards a showcase that has Chitti's body parts arranged. The guide tells the students that Chitti was the most advanced humanoid robot that was created twenty years ago and that it was dismantled due to "certain reasons". A curious girl asks why, to which Chitti's head responds saying, "I started to think". As the guide says bye to Chitti and takes them to another exhibit, the surprised student keeps looking back at Chitti in surprise .