Confocal laser scanning microscopy uses a focused laser beam (e.g. 488 nm) that is scanned across the sample to excite fluorescence in a point-by-point fashion. The emitted light is directed through a pinhole to prevent out-of-focus light from reaching the detector, typically a photomultiplier tube. The image is constructed in a computer, plotting the measured fluorescence intensities according to the position of the excitation laser. Compared to full sample illumination, confocal microscopy gives slightly higher lateral resolution and significantly improves optical sectioning (axial resolution). Confocal microscopy is, therefore, commonly used where 3D structure is important.