It may look crazy to an outside observer, but physicists nowadays shine a light on a wall and expect to see something behind it.
We propose to modify such light-shining-through-walls experiments in a way that some of the light will be allowed to go beyond the wall, i.e. the wall is not completely opaque. Then, if axions exist, we expect to see more atomic transitions when some of the light is converted to axions (in the presence of magnetic field) compared to a situation without axions. How much more? In a hundred days of experimental run a thousandth of a percent difference.
https://arxiv.org/abs/1803.09388
Caption: Set-up of the proposed experiment. The wall is not completely opaque, so some of the light (gamma_1) goes through. The axion (a) is created from the interaction of light with a magnetic field (B_1), goes easily through the wall.