Samples were observed either by dark field or epifluorescence microscopies: in the first case, an Eclipse Ni (Nikon) microscope working in reflection and equipped with a dark field condenser was used. The Nikon oil immersion microscope objective was 40× with a numerical aperture (N. A.) of 0.80. Images were acquired with an Iris 9™ Scientific CMOS camera (2960 × 2960 pixels) and further treated with ImageJ. Epifluorescence imaging was performed on a Leica DMI 4000B inverted microscope equipped with a ×40 lens (HCX PL APO, 1.4 NA) and a CoolLED light source combined with appropriate filter cubes to select the excited and emitted fluorescence wavelength range. Images were acquired using MicroManager and processed with ImageJ.