When San Diego-born baby girl Saybie was born in December, her parents were told she would have just hours to live.

Weighing a minuscule 8.6 ounces (245 grams), the tiny tot was believed to be the world's smallest baby.

Now, Saybie's story has been revealed for the world to know, and suffice to say it's truly incredible.

Born at 23 weeks, the tiny bub fought for her life as she was transferred to the intensive care unit at Sharp Mary Birch Hospital in California.

After being told she had hours left to live, Saybie's parents were left distraught – but what happened next was nothing short of miraculous.

When Saybie was born, it was believed she would have mere hours left to live.

In what might be one of the most incredible revelations, amazing images Saybie and her heartwarming journey against the odds has just surfaced.

As reported by the BBC, five-month-old Saybie has officially been discharged from hospital in the US.

Indeed a nurse who attended to the baby said the scenario was a "miracle".

The tiny bub weighed no more than an apple.

According to the Tinest Babies Registry, Saybie is thought to be the world's smallest surviving premature baby.

Saybie comes after another baby girl from Germany was born weighing only a smidgen more at 252 grams in 2015, according to the registry.

It is believed Saybie was the world's smallest surviving premature baby.

Saybie's mum gave birth to her via an emergency C-section three-months early – the unexpected procedure occurred after she was dignosed with pre-eclampsia, which is a condition whereby high blood pressure can be fatal to both the mother and her child.

A video produced by the hospital features the mother who describes the birth as the "scariest day" of her life.

"I kept telling them she's not going to survive, she's only 23 weeks," she said.

One nurse added: "You could barely see her in the bed she was so tiny."

But against all odds, little Saybie did survive, and her tale is nothing short of heartwarming.

That little face is utterly gorgeous!

As she spent her days in neonatal intensive care, a little pink sign by her crib read "Tiny but Mighty" – and it seems no other words could ring more true.

As Saybie left the unit this month, nurses perched a title graduation cap on her head.

While there is still a long road ahead for little Saybie, it seems her story is truly one to spark hope, with the hospital adding: "[She] experienced virtually none of the medical challenges typically associated with micro preemies, which can include brain bleeds, and lung and heart issues".