The cyclic growth and shrinkage of Wollastonite (CaSiO₃) particles in binary CaO-SiO₂ slags is investigated in-situ by means of high-temperature laser scanning confocal microscopy (HT-LSCM). The mode of cyclic phase transformations is chosen to avoid nucleation processes which would otherwise interfere with the kinetics of melting and solidification. The compositions of the liquid slags are carefully selected to induce different phase transformation conditions, i.e. congruent and incongruent melting. The evolution of the apparent surface area and changes in the morphology of CaSiO₃ particles during the cyclic heat treatment are observed in-situ. The cyclic growth and shrinkage of the particles is investigated by means of a sharp-interface model where the interfacial reaction and diffusion in the liquid bulk are considered as possible rate-controlling processes. The temperature dependent driving forces for dissolution and solidification are calculated by means of a recently developed Gibbs energy minimization algorithm. The experimentally observed growth and shrinkage of the particle area are compared to the simulated particle area. The kinetics of growth and shrinkage appears to be controlled by the interface reaction only in case of congruent phase transformations. Whereas, in case of incongruent growth and shrinkage of the particles both diffusion processes in the liquid bulk and the reaction at the interface determine the kinetics. The evolution of the microstructure during solid-liquid phase transformations of ceramics is investigated in this work from a fundamental and quite general perspective and promises to have a potential for future applications in materials design.