Book excerpt: Experimental equipment was developed for the light-microscopic observation of ferromagnetic domains by means of the Bitter technique. The design of an electromagnet-miroscope stage which can accommodate both bulk samples and thin sheet strips is described. The formula for the preparation of the colloidal iron-oxide solution is given. Photographs of domains on silicon-iron transformer sheet illustrate the quality of the pictures and the resolution which can be obtained with the set-up.