Building microscopes in the lab is a skill that is rarely taught at university. It is no coincidence that most people who have learnt to build microscopes have done so in the lab from other researchers or engineers. Usually, one needs to be lucky to find pieces of knowledge in random papers, in discussions with experts, or when browsing blogs like the one you’re currently reading. A part of the problem is that most papers that describe the novel design and construction of microscopes are often challenging to translate into practice even for experts because they describe the ideas and concepts and do rarely provide precise assembly instructions together with the rationale behind.

In their manuscript on An open-source two-photon microscope for teaching and research by Schottdorf et al., the authors go a different route. Instead of presenting a novel microscope design that shall be used for future experiments, they describe the rationale and principles behind a microscope design that was already used, tested and refined over many years in a very successful systems neuroscience lab.

The paper includes many interesting and useful pieces of knowledge. Among those, I would like to highlight only a few:

• The assembly instructions and rationale for a custom scan lens and tube lens based on off-the-shelf components (see the Results section, but also the Discussion with comments on ideas from astronomy and photography).

• A similar design suggestion and analysis for the detection path.

• A discussion why an axial FWHM of 5 μm is, in the view of the authors, a pragmatic compromise for in vivo-imaging with movement artifacts.

• The interesting side-note that ±28 V instead of ±24 power supply specifications are advantageous for galvo scanner performance.

• The measurement of the dispersion for this specific two-photon system, which can be considered typical for two-photon microscopes (approx. -20000 fs²).

In addition, the manuscript comes with a very nice documentation on Github that includes a detailed assembly protocol, a list of parts including prices of laser, objective, shutter, power meter, PMTs, etc.

Altogether, a great resource that is definitely worth a look.