Among all the hazy New England IPAs, trendy sours, and special releases out there, one year-round beer has captured the hearts and minds of beer lovers: Heady Topper from The Alchemist. This is a unicorn beer with limited distribution, and it’s on nearly every craft beer drinker’s bucket list. Here’s what you need to know about Heady Topper.

It is what it is today because of a flood.

Heady Topper’s origin story begins at The Alchemist Pub and Brewery in Waterbury, Vermont. It flooded in 2011 after Tropical Storm Irene, shortly after John and Jennifer Kimmich had purchased a canning line. The two decided to transition from a restaurant that poured Heady onsite to a beer that claims it’s at its best in a can.

John Kimmich got his start working for free at a brewery.

Kimmich graduated from Penn State in the mid-1990s and worked at the Vermont Pub and Brewery in Burlington. Greg Noonan, a home brewer and writer, trained Kimmich on the technical aspects of beer making for a year on the weekends.

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Heady Topper was originally only made two times a year.

When Kimmich first started brewing the beer, he made it alongside other beers he was serving at Alchemist Pub and Brewery. The super-hopped Heady Topper started getting more attention over time, though, and Kimmich devoted more time to brewing it.

People used to bottle Heady in the bathroom — illegally.

For a while Heady Topper was only sold on tap at the brewpub, so customers would take their pints into the bathroom, pour it into a bottle, and leave, according to Longreads.

The first cans of Heady Topper came two days after the flood.

Jennifer was the driving force behind canning the beer, and they got to canning just two days after The Alchemist Pub and Brewery was destroyed.

One particularly dedicated drinker flew in from South Africa just for a couple of cans.

People do crazy things for rare beer. Alchemist had to limit on-site sales of Heady Topper shortly after starting the canning line to make sure it could supply to retailers, and beer tourists flocked to stock up on as much as they could. One family took their private jet from South Africa just for some beers.

Heady Topper uses an extremely rare yeast that only The Alchemist has.

Greg Noonan, the man who taught Kimmich how to brew, gave Kimmich yeast he got in the 1980s in England and made Kimmich promise he wouldn’t share the original culture. Other known ingredients includes British barley and American hops, particularly Simcoe.

Heady Topper is designed to be drunk from the can.

Kimmich told Longreads that Heady Topper dies as soon as it’s poured into a glass.

“All that carbonation is coming out, the CO2 is escaping, the aroma, the hop essence, and oils,” Kimmich said. “When you drink it out of the can, the beer is perfectly preserved. There’s a layer of CO2 riding through that can, and when you pour the beer into an empty glass, you’re immediately accelerating the expulsion of all that goodness.”

There was an entire website devoted to where people can buy Heady.

A website called Heady Spotter started up after The Alchemist was forced to stop on-premise sales because crowds were blocking roadways. The website had the stated goal of “democratizing the hunt for the most elusive beer in the world,” and listed delivery routes for each day of the week. After production of Heady Topper increased and the beer became somewhat easier to find, Heady Spotter shut down. On March 9, 2017, Heady Spotter tweeted its last tweet: “With the bigger brewery online and ample supply of amazing #vtbeer, this account has successfully completed its mission.”

It’s still growing.

The Alchemist opened a second production facility in Stowe, Vermont in 2016. The second location brews Focal Banger, another big IPA, and seasonal beers, but it also sells Heady.

There are 24 buying locations.

On The Alchemist website, people interested in buying some Heady are directed to a “where to buy” page with 24 locations and the day the locations receive their shipments.

A woman was arrested for selling Heady Topper online.

In 2013, a woman was arrested for selling cases of Heady Topper on Craigslist — for $825.