Finally, the developing brains are enveloped in a blanket of jelly. “It’s the opposite of normal jelly – it starts off as a liquid which you pour on and it jellifies as it warms up in the incubator,” she says. The jelly mimics the tissue a brain would normally be surrounded with in an embryo – like a makeshift skull – and encourages them to develop relatively normally.

Then all you have to do is sit back and wait. Three months later, the finished product is about four millimetres across and contains around two million neurons. “A fully developed, adult mouse brain only contains four million, so you can do a lot with that number,” she says.

The brains are constantly buzzing with electrical activity as neurons zap off signals to one another – though Lancaster says this isn’t much of an achievement on her part. “It’s not very special but it does tell us that we are making functional neurons and that they are acting like neurons,” she says.

She compares it to the heart cells which scientists coaxed to beat inside a petri dish back in 2013; while heart cells are programmed to “want” to pump, neurons “want” to fire. “Even if you have a neuron by itself in a dish with no other neurons, it wants to fire so badly that it will connect to itself in order to fire,” she says.