Optical microscopy can be used in the study of colloidal systems, however, more advanced methods like transmission electron microscopy (TEM) and atomic force microscopy (AFM) are often used to characterize forms of soft matter due to their applicability to map systems at the nanoscale. These imagining techniques are not universally appropriate to all classes of soft matter and some systems may be more suited to one analysis over the other. For example, there are limited applications in imagining hydrogels with TEM due to the processes required for imaging, however, fluorescence microscopy can be readily applied. Liquid crystals are often probed using polarized light microscopy to determine the ordering of the material under various conditions, such as temperature or electric field.