Confocal scanning laser microscopy (CSLM) was first developed and used for in-situ high temperature observations by Emi and co-workers at Tohoku University. Today the technique has applied widely in high temperature metallurgical research. During last decade, the results have been achieved at the University of Leuven. These include: (1) in-situ study of high temperature behavior of complex ceramic materials, (2) oxide particle dissolution in the molten slag, (3) inclusion behavior in the liquid steel, (4) chromium carbide precipitation in stainless steel; (5) graphite precipitation behavior in cast iron, (5) solidification or crystallization behavior of metallurgical slags, (6) in-situ observation of alloying and deoxidation of steel, and(7) phase transformation and melting of steel. In this lecture we highlight some of our current work, including in-situ observation of (I) the slag solidification, (II) formation and interaction behavior of steel inclusions, and (III) rare earth oxide dissolution in molten salts.