Maya Parker was in Central City, you know that day when the particle accelerator exploded.
She had been waiting that day, waiting for a friend, who in the end never showed. She was disappointed, and annoyed, like what a friend she had, leaving her on the sidewalk in the rain.
That's when she started to think to herself.

What if she had super powers, "I wish I could just fly home" she thought to herself. "Ew what if I could just teleport home" she thought, as she continued to think of weird ways she could possibly get home.
"What if I could do whatever I need to do to get whatever I need to do done" she thought "what if I had powers whenever I wanted to do whatever, to do anything, something meaningful" she thought and then it happened, the particle accelerator exploded.
It scared Maya so bad she slipped, hitting her head on a concrete wall, before it hit the sidewalk. She was out, out cold. 
She was just one of the Meta humans who were "born" that day.  But she didn't realize she had powers right away.

Let's just say she finally realized how challenging things had gotten for her, controlling her powers in all, she went to S.T.A.R Labs, where she started to question her purpose in life. She watched Caitlin treating a young man, handsome too, who was struck by lightning the day of the explosion, the day he almost lost his life too.

Then there is Barry Allen, the CSI who was shocked by lightning that night when the accelerator exploded.

He almost died, and when at the hospital, they thought he was dead, and then Wells stepped in, convincing Joe West, the father figure in Barry's life after his father went to jail for murdering his mother, to let him take Barry to S.T.A.R Labs where he would take care of him along with the help of his colleagues, Caitlin Snow, and Cisco Ramon.

And that's where the heroes stories start, and where all the Meta humans stories start,
S.T.A.R. Labs, particle accelerator explosion, that day changed everything, the lives of a lot of people.

And in Barry and Mays's cases, it changed for the better, because they met each other. To better explain the ending let's just say I don't know, maybe they end up together.