Everybody knows John Krasinski as the adorable heartthrob love interest Jim Halpert on NBC's acclaimed sitcom, The Office. Many also know him from the thrilling Amazon series Jack Ryan, where he plays the titular character, Tom Clancy's famed spy. And, of course, he's now also well known for starring in the hit horror movie A Quiet Place, which he both wrote and directed. He starred in this film with his equally famous (and gorgeous) wife, Emily Blunt.

It's clear that John Krasinski is a big star now, but he wasn't always like this. In fact, he once had wildly different career aspirations, and at one point he was a few weeks away from giving up on acting for good. Read on to learn more about how John Krasinski became the star we know him as today.

15 He Grew Up In Boston

John Krasinski was born in St. Elizabeth's Hospital in the Brighton neighborhood of Boston, on October 20, 1979. He grew up in Newton, a suburb of Boston, southwest of the city. He's still loyal to his Massachusetts roots and is an avid Red Sox fan: He even appeared in a Boston-themed Super Bowl commercial this year, with several other stars, including Chris Evans!

14 His Mom Is A Nurse And His Dad Is A Doctor

Krasinski was born to parents Mary Clare and Ronald Krasinski, both medical professionals. His mother, Mary Clare, was a nurse, while his father, Ronald, was an internist. An internist is a type of medical doctor that focuses on things that are going on inside the body, like issues with internal organs.

13 He Has Two Older Brothers

In The Office, Krasinski's character Jim has two older brothers who love to prank him (and aren't that great at it). As it turns out, he may have been able to draw on his real-life experience for that, because the actor really does have two older brothers! Their names are Paul and Kevin Krasinski, and while we don't know if they were particularly pranky with each other, they probably did each other a fair amount of mischief growing up.

12 He Went To High School With A Fellow Office Star

That's right! John Krasinski attended Newton South High School with B.J. Novak, one of the writers for The Office, who also played the character Ryan Howard. These two didn't only attend school together: They were friends too. Before they both graduated in 1997, Krasinski starred in a satirical play that Novak wrote and directed. The two had no idea they had been cast in The Office together until they showed up for shooting. What a small world!

RELATED: Jenna Fischer And John Krasinski Hit It Off Immediately On The Office

11 He Taught ESL In Costa Rica

When he was 17, the summer before he went to college, Krasinski decided to go and teach English as a second language at a school in Costa Rica. He described his time in Costa Rica as incredibly transformative, but it wasn't teaching English that did it - it's because he saved a girl from a riptide while swimming there!

“Granted, not everybody needs to have life-or-death experiences, but that changed my entire life. All of a sudden I grew up."

Very Jack Ryan of you, John.

10 He Went To Brown University

In case it wasn't obvious from his masterful writing and directorial skills, John Krasinski is a very smart man. He even attended an Ivy League school - Brown University in Providence, Rhode Island. He majored in English, and graduated with honors in 2001.

What's interesting about it though, is that he was a late admission! He was wait-listed, and then accepted in January instead of August the year he started.

9 He Wanted To Be An English Teacher

Going into college, Krasinski had designs of being an English teacher, the kind who wears "corduroy jackets with patches on the elbows." (Apparently, his time teaching in Costa Rica had a big impact, too.) So in some alternate universe somewhere, there is an English teacher in a high school who looks like this...and his students are all very lucky.

8 He Graduated A Playwright

A Quiet Place was far from Krasinski's first attempt at authoring a script. For his honors thesis, his final project at Brown University, he wrote a play called "Contents Under Pressure," about a tense exchange between a man whose father has just passed away, and a random passerby. He dedicated the play to his parents, saying "you guys have forever been good sports and true inspiration for happiness." Aw!

RELATED: 15 Things You Didn't Know About The Making Of A Quiet Place

7 He Went To Acting School For Fun

Because Krasinski was admitted to Brown late, he still had a semester to go after all of his friends graduated in May of 2001. So, assuming he was just going to be an English teacher, he decided that he just wanted to find a school that would transfer the credits he earned there back to Brown after his final semester. He chose the National Theatre Institute in Waterford, Connecticut, and after his time there he told his mother that he wanted to move to New York to become an actor.

6 He Also Studied At The Royal Shakespeare Company In England

After he got hooked on acting at the National Theatre Institute, he had some catching up to do to get his acting on par with the rest of his peers, most of whom had had acting training at least through college, if not longer. To remedy this, Krasinski sought acting training at the Actors Center in New York, as well as the prestigious Royal Shakespeare Company in England.