Kenyan science teacher, Rose Tata Wekesa, appears to have broken the world record for the longest non-stop science lesson.
The classroom laboratory, in the Kenyan capital, Nairobi, erupted into loud cheers as the clock reached 50 hours.
But Ms Wekesa was not finished and has pressed on beyond the 50-hours target. The record will now need to be verified by Guinness World Records.
She is a biology and chemistry teacher at St. Austin's Academy, an international school in Nairobi.
Last month she told the privately owned Citizen Digital news website she was undertaking the challenge because she wanted "to show the doable and interesting side of science".
She added: "I want to motivate young ones in school who want to become teachers by showing a teacher can achieve greater things beyond the classroom."
Her attempt is currently being livestreamed online and is taking place at the Multimedia University in Kenya.