In a thermal system, fluctuations of particle yields are directly encoded in the equation of state of the system under the study. By measuring event-by-event fluctuations over an ensemble of events via cumulants or moments of particle multiplicity distributions, one can study the freeze-out conditions in heavy-ion collisions and clarify their relation to the QCD phase transition.
In this contribution, recent studies of measured event-by-event fluctuation signals of identified pions, kaons and protons are discussed. The experimental results are confronted with corresponding signals from dynamical models, and the dependence of fluctuation measurements on phase-space coverage of detected particles are addressed in view of the calculations from Lattice QCD (LQCD) and the Hadron Resonance Gas (HRG) model. Moreover, several experimental challenges, such as particle detection efficiency losses, volume fluctuations etc., for the measurement of fluctuation signals are briefly discussed.