The most important tool in neuroscience is a multiphoton rig in 2020. If we ask why, the answer is relatively easy, because it is non-invasive and it is able to use for functional imaging. In a recent study Wang and his colleagues showed a new method to examine the mouse without any surgery. They could image the cortex with a decent spatial resolution even in the deep regions. Three-photon excitation (3PE) is a great tool to revolutionize the functional imaging in the neuroscience.
The attached figure shows a comparison of through-skull vasculature imaging by 3PM and 2PM.
Original publication: Wang, T., Ouzounov, D.G., Wu, C. et al. Three-photon imaging of mouse brain structure and function through the intact skull. Nat Methods 15, 789–792 (2018)