One of the people I've been following since Test Tube was launched is Professor Seamus Garvey from The University of Nottingham.
He has a grand plan for energy storage.
In a nutshell, he wants to build giant wind turbines with pistons inside their blades. The pistons compress air, which is then stored under the sea in giant "air bags".
The highly compressed air is then released and converted to electricity as it's needed.
It was just an idea when I first met Seamus... But over time we've seen him build models and protoypes.
There's a still a long way to go, but following projects like this has been one of the highlights of the Test Tube video project - really going behind the scenes in the world of science and engineering.
This week's video saw Seamus testing a version of the piston.
And not long ago we were there to see the air bags for the first time.
I've also created this video player which shows all the videos I've made about Seamus so far!
I wonder what's next?