(A) Photograph of the LED illumination system attached to the microscope. Red and a blue LED are arranged in a square. Each side of the square can be switched on/off individually for directional lighting. (B) Photograph from the sample side. (C) Schematic of the LED square arrangement. Each side is tilted by 60° toward the sample. We provide the board design file in the Supplementary file 1. (D) Schematic of the circuit diagram of one side of the lamp. LED: light-emitting diode, R: resistor, T: transistor, JP: pinhead. (E) The emission spectrum of the lamp. (F) The voltage can be adjusted in the range of 3.5–9.5 V. Resistors used to reach light intensities ranging from 40 to 180 μmol/m²/s: R1-8: 220 Ohm, R9-12: 1220 Ohm. (G) Single optical section recording of a lateral root primordium expressing GFP-plasma membrane marker UBQ10::YFP-PIP1;4 and RFP-nuclear UBQ10::H2B-RFP marker. Green fluorescence was collected between 490 and 576 nm, red fluorescence was collected between 560 and 700 nm. The fluorescence intensity profile of the yellow line (21 px width) is plotted in (H). (H) Intensity profile along the yellow line shown in (G) of the red and green channels with illumination system switched on or off, respectively, demonstrating that RFP/GFP imaging is not affected by the illumination.