Caster Semenya has testosterone levels three times higher than normal women and was forced to undergo gender testing after a successful season in 2009.
She was cleared to compete but during the London Olympics in 2012, she was forced to take testosterone suppressants by the AIFF and she won silver in the 800m.
But last year, an Indian athlete successfully challenged the AIFF's treatment for hyperandrogenism and the rule was subsequently dropped.
So this time, she's running without testosterone suppressants, and that's what all the fuss is about.
Because of her rare condition, she doesn't have a womb or ovaries and has internal testes.
Officials are so worried about the hostility towards her, she has personal bodyguards around the clock and nobody except her coach and team-mates are allowed near her.
Bars and cafes were packed with fans anxious to witness the start of her campaign for gold.
She's been subjected to hundreds of hate messages on social media and in return, she posted on Instagram "To all the haters, I have so much more for you to be mad at, just be patient."
I hope she wins.