The fluorescence measurements were performed on a fully motorized inverted wide field microscope (Nikon Ti-E or Ti-2) equipped with an environmental box which was pre-heated to 30 °C and maintained at this temperature during the whole cultivation time. The microfluidic device was mounted on the microscope using the in-house made holder, allowing an addition of the magnet holder on the top of the microfluidic device.31 (link)The individual compartments were imaged for a 15 h period (10 h every 30 min, 5 h every 1 h) by brightfield and fluorescence microscopy through a 10× objective (Nikon Plan Fluor). Lumencor Spectra X LED was used as a light source for fluorescence excitation (25% of the maximum light intensity) with corresponding optical filters and dichroic mirrors (riboflavin: cyan LED, 475/28 excitation filter, 495 dichroic, 525/50 emission filter; mKate2: green LED, 549/15 excitation filter, 562 dichroic, 593/40 emission filter). The fluorescence and bright field images were recorded by a Hamamatsu Orca Flash 4 camera (exposure times: 20 ms bright field, 100 ms fluorescence). The microscope was controlled with the NIKON NIS-Elements Advanced Research software. The time-lapse images were acquired using the Nikon Perfect Focus System.