On Monday, physicist (and father of the Xbox) Seamus Blackley used 4,500-year-old yeast to bake a loaf of sourdough.

He chronicled the whole endeavor on Twitter, from extracting spores from ancient Egyptian pottery straight to the finished loaf. To his surprise, thousands of people liked and shared the thread, fascinated by the intricacies of the ancient bread baking techniques that Blackley is an amateur expert in.

The bread eaten by ancient Egyptians is a lot different than what we eat today, but Blackley has been working to recreate it. He had already taught himself how to bake sourdough with freshly milled Barley and Einkorn, ancient grains that few modern people still use, which he also documented on Twitter. But there was one crucial ingredient he couldn’t get at any supermarket: ancient yeast.

According to Blackley, yeast is what gives bread its flavor, but the yeast that we use now is significantly different than ancient yeast. The yeast you buy at a grocery store is bioengineered, but Blackley has taken to collecting yeast the old fashioned way: by leaving a flour and water mixture out in the woods and collecting microbes from the environment. The problem is, our atmosphere has changed a lot since the ancient Egyptians were baking, and microbes have changed with it.

To make authentic ancient Egyptian bread, Blackley had to get his hands on some of that ancient Egyptian yeast. Luckily, most of the yeast used in breadmaking hibernates for long periods of time, so he started looking for ancient yeast in Egyptian pottery like the kind held by museums.

With the guidance of microbiologist Richard Bowman of the University of Iowa and archeologist Serena Love of the University of Queensland, he traveled to the Boston Museum of Fine Arts and Harvard’s Peabody Museum to collect yeast from ancient egyptian pottery used for breadmaking.

With the museum’s blessing, the researchers extracted the yeast trapped within the pores of the clay. Without damaging the artifacts, they pumped liquid in and pulled the yeast out with it. “Our extraction process was basically a form of microbiological fracking,” Blackley said.

A lot of those samples were shipped to a lab, Blackley said, where the researchers plan on doing genetic testing to understand more about this ancient yeast. In the meantime, though, Blackley took one sample for himself to create a sourdough starter.

Using sterile lab techniques in his home kitchen to avoid contamination, he fed the yeast ancient grains for a week, culturing it until it was ready to bake. On Monday, he put the yeast to work. He baked a sourdough loaf, with a hieroglyphic carved into the final product.

He said that it smelled “much sweeter and more rich” than modern sourdough bread, and tasted amazing.

“I had to stop myself from eating too much because it was one in the morning,” Blackley said.

The next step for Blackley is baking like the Egyptians, over a clay baking pit, he said.

Blackley said that researchers are doing DNA sequencing right now to verify the results, but the pottery they got the yeast from was 4,500 years old. However, until they get the sampling back, they won’t know for sure that the yeast wasn’t contaminated by other, less ancient strains. They’re comparing the samples against an actual loaf of ancient bread, also preserved at the Museum of Fine Arts.

To Blackley, trying to bake like Egyptians isn’t just a scientific curiosity. To him, baking represents a cultural connection to the past. Though he can learn a lot about ancient cultures from museum exhibits, to be able to cook like them allows Blackley to “virtually break bread with them.”