Reflection interference contrast microscopy. (A) Scheme depicting RICM image formation at the cell-surface interface. I1 and I2 are the intensities of the light reflected on the glass-buffer and the buffer-cell interface. The interference between these rays is measured. (B) RICM image (top) and brightfield image (bottom) of a cell. The RICM image displays different grey levels, which correspond to differences in the distance of the cell membrane to the glass interface. Darker areas represent close distances between the cell membrane and the glass interface, in other words, areas of cell adhesion. In addition, small cellular filopodia that are invisible in the brightfield image can be visualized with RICM (see image enlargements).