Modulated differential scanning calorimetry (MDSC) is a recently developed extension of DSC that adds a new dimension to the conventional approach. The usually linear temperature programme is modulated by a small perturbation, in this case a sine wave, and a mathematical treatment is applied to the resultant data to deconvolute the sample response to the perturbation from its response to the underlying heating programme. In this way the reversible (within the time scale of the perturbation) and irreversible nature of a thermal event can be probed. The advantages include disentangling overlapping phenomena, improving resolution and enhancing sensitivity. A further benefit is that metastable melting can be detected in cases where it is not normally observed. This new technique offers considerable scope for further development.