Chemistry remains relatively closed to the blind, due to the hazards of laboratory work, and the ubiquity of images, charts and graphs. But chemistry teacher Tobias Mahnke, who taught Portz at the Blista-associated Carl-Strehl-School in Marburg, argues there is no reason why his subject should be so restricted.

”No human being can see molecules, no human being can see atoms, and yet, chemistry education is so visual. Why? There shouldn't be any disadvantage for blind people, given that sighted people can't see all this, either," he says.

"Most scientific experiments go far beyond seeing. You can touch things, something becomes warm or cold, you can smell and hear things, and in experiments with food, taste them," says Mahnke as he shows the models via video. "In regular teaching, we focus on vision because it means I can demonstrate an experiment within five seconds, and it can be seen by 30 students. It's fast and efficient for the teacher, but not for the pupils."

Around the world, blind innovators are slowly dismantling some of those barriers. The chemist Mona Minkara is designing an inclusive STEM curriculum, the computer scientist Chieko Asakawa is developing accessible artificial intelligence, and the astronomer Wanda Díaz-Merced is using sound to study space, to name just some.