Maggie Pierce

Margaret "Maggie" Pierce was hired as Head of Cardiothoracic Surgery at Grey Sloan Memorial Hospital after Jeff Russell quit. Shortly after starting work, she revealed to Richard Webber that Ellis Grey is her birth mom.

Education
Margaret is very driven and finished both high school and medical school faster than normal.

Search for her Birth Mom
Two weeks after she was hired as head of cardiothoracic surgery at Grey Sloan Memorial Hospital, Margaret told Dr. Richard Webber that she was adopted, and that 2 years prior, she looked for her birth mom and needed to go to the court for the records. She found out that she was dead, but got her name, and discovered that she was an amazing surgeon that worked at the Seattle Grace Hospital, now Grey Sloan Memorial Hospital, Margaret's current workplace. She stated that that's not why she took the job, but it's "a little bit" why she was interviewed. When Richard asked Margaret what her mother's name was, she said that it was Ellis Grey. ("Fear (of the Unknown)")

Working at Grey Sloan Memorial
Maggie quickly began to integrate into the hospital, getting to know everyone and how things work. However, she butted heads with Meredith Grey over a case. This came to a head when Maggie told Meredith that Ellis Grey is her birth mom. ("Puzzle With a Piece Missing")

Personality
Maggie describes herself as a big control freak, resulting in a great professional drive and her being unable to leave things unfinished. She is also described as perky and chatty, often putting her in awkward situations when she's not up to date on other people's personal life.

Romantic
She dated a man named Dean who loved to cuddle. But since she can't sleep with someone lying next to her, she would sneak out after he fell asleep and spend the night on the couch before returning in the morning before he woke up. He eventually proposed and she explained the sleeping to him, telling him he could sleep in a room down the hall. It didn't work out and he is now married to a woman who loves cuddling. ("The Bed's Too Big Without You")

Parents
She describes her parents as good, funny, kind, and goofy. About two years after she started working at Grey Sloan Memorial Hospital, her mother confessed to her that she'd been having an affair with their car serviceman for 11 years and they had only stayed together for her sake, but were getting a divorce now that she was out on her own.

Grandparents
All her grandparents are still living.

Ellis Grey
Margaret never met her birth mother, but 2 years prior to joining the Grey Sloan Memorial Hospital staff, she looked for her birth mother and found out that she was dead, but got her name. After learning that Maggie is her half-sister, Meredith gave Maggie Ellis's journals, so Maggie could get an idea of what Ellis was like.

Richard Webber
Margaret met her birth father unknowingly when she arrived at Grey Sloan Memorial Hospital. Maggie quickly bonded with Webber while they worked together. She admired his skill greatly. When he eventually tried to tell her that he's her biological father, she became upset with him for having not told her right away.

Meredith Grey
Meredith and Maggie didn't get along at first. They fought over little things and about patients. Derek planned a family dinner for himself, Meredith, Maggie, and Richard but he and Meredith ended up having sex in the shower and missing the dinner, hurting Maggie's feelings. ("Don't Let's Start")

When Meredith confronted her about it, she told Meredith that the reason she was sad about the dinner being canceled was because she was excited to talk to people and eat food that wasn't from a packet and socialize. Meredith then invited Maggie to Ellis's old house to socialize with Callie and Alex. ("Could We Start Again, Please?")

Cristina Yang
Cristina and Margaret first met when Cristina interviewed Margaret for the head of cardio position at GSM. Despite feeling that Maggie was very young to do the job, she admitted to Owen that she was qualified to do it.

Once she was officially hired, Margaret became frustrated because Cristina didn't respect her as her new boss. On Cristina's last day, she scheduled a pediatric heart transplant (for Link McNeil) amidst the chaos of the explosion at the mall, much to Maggie's confusion and frustration. Cristina even treated her as a resident by not listening to her objections and practically forcing her to prepare Link for the surgery. Margaret ultimately did the transplant herself as Cristina had to leave to catch her flight.

Career
She is the new Head of Cardiothoracic Surgery at Grey Sloan Memorial Hospital. She finished high school and med school early, and already led her own department for two years before moving to Seattle.

Notes and Trivia

 * Maggie finished high school and medical school early.
 * In the episode, Fear (of the Unknown), it is revealed that her birth mother was Ellis Grey and therefore, Meredith Grey is her biological maternal half-sister.
 * Her biological father is Richard Webber.
 * The writers stated they knew about Maggie's existence since the very beginning and wanted to introduce the character ever since season 4, but chose to introduce Thatcher's other children first; afterwards, it never felt like the right time until Cristina left, creating a hole in Meredith's life. This also led Shonda to claim that there have been indirect references to Maggie over the course of the series. This is especially evident in season 3 as Only Mama Knows features numerous flashbacks from that season.
 * There's nothing Maggie doesn't eat.
 * On Twitter, Shonda Rhimes revealed she thought a lot about making Ellis and Richard's love child a son. She even looked for an actor, but decided to settle for Kelly McCreary's acting talents, as the actor's great acting skills were more important to her than the actor's sex.
 * Her salary is $126,000/year.
 * Her employee ID number is 6654.
 * Her work email address is mpierce@greysloan.
 * Maggie is very accomplished for her age: despite being five years younger than Meredith, Maggie had already been a cardio chief for two years prior to her employment at Grey Sloan Memorial Hospital, board-certified, and a Fellow of the American College of Surgeons.
 * She can't sleep if anyone else is in the bed with her. ("The Bed's Too Big Without You")
 * She was a girl scout. ("All I Could Do Was Cry")
 * She was registered with a babysitting service as a teen. ("All I Could Do Was Cry")
 * She had a full genetic history done when she was 12. It revealed a genetic predisposition to Alzheimer's disease. ("Don't Dream It's Over")

Notable Episodes
These episodes are Maggie-centric or are otherwise very informative about her life.
 * Fear (of the Unknown)
 * Puzzle With a Piece Missing
 * Only Mama Knows

Memorable Quotes

 * Maggie: You think I look too young. I finished high school early, also med school. Pretty annoying, right?