Green energy storage will become necessary. We can store energy in a battery by charging it. Similarly, we can apply electricity to an electrolysis cell to store energy as a fuel. I am using powerful electron microscopes to analyze structures in electrolysis cells all the way down to the atomic scale, but today we can only do this with inactive cells. In HEIST, we will develop a new method that will allow us to perform electrolysis experiments with tiny cells, inside an electron microscope. With such a method we can do electrolysis while looking at the active sites. We can answer key questions about important dynamics in the cell, and in this way accelerate the development of electrolysis cells to be implemented in a green energy infrastructure.