High temperature confocal laser scanning microscopy (HT-CLSM) provides the opportunity to perform in-situ direct observations of e.g. crystallization, solidification, phase transformation at high temperatures for materials, such as metals and ceramics. The investigated sample is positioned in a crucible, placed on a specimen stage with thermocouples attached for temperature control. The furnace is heated by a halogen infrared lamp, and the sample is placed at the focal point of the infrared beam which is reflected by the gold coated ellipsoidal furnace chamber. The imaging of the sample surface is conducted with the use of a He-Ne scanning laser beam and a confocal pinhole aperture enabling excellent contrast and resolution along the laser beam direction (Z direction). The laser power is about 1.5 mW in general and operates in the red, blue and violet wavelength range. When performing Z scans 3D reconstructions of the surface can be constructed, but for fast imaging of e.g. phase transformations Z scanning is not adjusted much, instead the surface relief between parent and product phase is observed at the almost fixed Z distance in real-time.