In 2010, Ms Stella Chua went through about a month of check-ups and other medical procedures to donate bone marrow to a complete stranger.
The year before, the 24-year-old nursing student had registered to be a donor at a blood drive, which had a booth set up by the Bone Marrow Donor Programme, a non-profit organisation which runs a register of donors.
Ms Chua was there with her mother, Madam Ong Soh Kim, a 53-year-old housewife, to donate blood. Her mother wanted to register but was turned down because of her age. She encouraged her daughter to sign up instead.
Madam Ong says in Mandarin: "Many years ago, I read in the newspapers about a girl who was saved by such a donation. It is a kind act that can save a life."
Ms Chua adds: "I didn't know much about giving bone marrow, but I agreed that it could help someone.
"So I filled up a form, and in less than five minutes, a staff member pricked my finger to take a blood sample. After that, I carried on with my life."
Half a year later, she was told that her bone marrow was a match to a cancer patient's. Over the next month, she went for check-ups, X-rays and blood tests to ensure that she was fit to donate bone marrow.
Before it was harvested, she had to have injections which made her body ache, but which she described as being "not really painful".
The harvesting was a three-day outpatient procedure. Ms Chua spent about seven hours a day hooked up to a machine in a hospital. She was put under local anaesthesia.
She says: "I wasn't bothered by any of this. I am not afraid of needles and I even fell asleep during the harvesting."
Last August, she met the patient she saved, Madam Stacey Lim, a 40-year-old housewife, for the first time at a get-together event for cancer survivors and hospital staff. It was held at a multi-purpose hall in the Singapore General Hospital.
Their meeting was a coincidence. Ms Chua was a volunteer at the event and Madam Lim was there as a guest.
At the event, Madam Lim was told by a hospital staff that there was a chance she could meet her donor.
While waiting for the staff to seek Ms Chua's consent, Madam Lim rushed to a nearby bakery and bought a box of mini mooncakes. She darted into a convenience store to buy a card and scribbled a thank-you note.
The pair eventually had a tearful meeting on stage. They hugged and were overwhelmed by tears.
Madam Lim says: "I was already crying before we met. I wanted her to know how grateful I was. It was either get a bone marrow transplant or die."
Ms Chua says: "I had received an update that the recipient of my stem cells was stable but I did not know how she was doing. I was very happy to see that she was strong and able to function normally."
In October 2009, Madam Lim was diagnosed with Acute Lymphoblastic Leukaemia, a type of cancer that affects the bone marrow. She had been given three to six months to live. The odds of a match were one to 20,000.
The mother of two was prepared for the worst. Her son and daughter are now 12 and 14 years old. She is married to Mr Eric Low, 40, who is self-employed.
After that first tearful meeting, Ms Chua and Madam Lim met again at a charity event organised by the Bone Marrow Donor Programme. They spent about two hours chatting. Now, they keep in touch through text messages.
Madam Lim returned to her daily routines about a year ago but still goes for check-ups at the hospital several times a year. She plans to take Ms Chua and her family out for dinner soon.
She says: "I was not hopeful when the doctors told me the odds and I was mentally prepared that I would not survive. Stella has given me a new lease of life."