Nico Robin is the daughter of Olvia Robin. Olvia left to go on an archeological expedition when Nico was only two, and this caused her to go and live with her aunt and uncle. Now it sounds cruel to leave Nico (and it kind of was), but the archeologists of Ohara were the best of the best (extremely dedicated).
Her aunt saw her ad nothing other than a burden, and so she was basically treated basically as a servant (Cinderella if you know the movie). It is during these years she apparantly ate the Hana-Hana no mi to get her powers.
So at the age of 8 she is able to pass the Oharan exam, and became an official Archeologist with the hopes of working on Poneglyphs with the other Archeologists as they were the only people who were nice to her. Sadly, their fear of what would hsppen were they caught (AKA: execution) led to them saying she couldn't work with her....she leaves crying.
She runs to the beach where a washed up giant named Jaguar D. Saul is. He at first tries to scare her away, but Robin being Robin just stares at him. He eventually asks her to not tell anyone. When she agrees he says, "Yeah right I'm a giant!" But she informs him she only has an interest in the Void Century. This greatly shocks him....
During the next few days Saul is building a raft to leave the island (as he is being chased). He eventually completes the raft and is about to go, but seeing Robin saddened he decides to build a flag as an excuse to make her smile.
During this time Nico's mother Olvia returns to the island knowing the Marines are in close pursuit. She goes to warn the other Archeologists. Basically we find out her group was attacked, and she was the sole survivor. We also find out that Jaguar D. Saul was a former Vice Admiral. The navy of CP9 arrives under the control of Spandene (Spandam's father), and round up the Archeologists.
Robin returns from Saul around this time and out of a desire to be with her Archeologist friends she says she is one too. Now this is when Olvia is being led away from the arrested Archeologists....this brings one of the most touching moments....Nico calls out asking if she is her Mother to which Olvia says no...she is crying, but her back is to Nico so she can't see.
At this time Spandene gets pissed and calls the Buster call. He didnt quite get what it was do he runs for it leaving behind Olvia as the Marines start bombarding the island regardless of who is on it. The Archeologist tree catches fire so they all go and try to save the books (a futile effort). Nico finally meets her mother and Olvia thanks her for calling her Mother....Saul then arrives and Olvia (whom he abandoned the Marines to help because he thought it wrong to kill Archeologists when they committed no real crime), and she asks him to get Nico out of here. She and the other Archeologists then die trying to save books as the tree colapses.
Now the normal villagers are being put on a boat as the Buster Call is supposed to only Target the Archeologists and the island. Saul tells Robin to get on and then goes to attack some of the ships causing a diversion....badass picks up some boats. Akainu being the Red Dog douchbag blows up the civilian boat killing all the people on it because he had to make sure no Archeologist escaped....this greatly shocks Aokiji (who is another Vice Admiral summoned vis Buster Call), Saul (almost thinking Robin died), and Robin who was didn't get on when she realized all the people she loved weren't on that boat.
Upon seeing Robin alive Saul goes to get her out, but eventually Aokiji catches him (it is around this time the boat is blown up shocking them all). Aokiji begins freezing Saul and he tells Robin to run and use his raft. He tells her she has to go on living, and to laugh when it is hard (he has a unique laugh Dreshishishi). He tells her eventuslly she will find her Nakama that won't abandon her.
Robin makes it to the raft where Aokiji waits....he majesty a path with ice telling her it leads to the nearest island. H spares her because Saul had been his friend, and after this he would hunt Robin down. Robin then leaves the burning Ohara in tears using Saul's unique laugh as it is supposed to make her happy.
Finally she is seen working for various pirates and getting rooted out in attempts to get money from her bounty.
That is the past of Novo Robin. That is why she is awesome, and part of the reason she's my favorite Straw Hat