Type-I ELMs [1­3] are regarded as a possible method to control the plasma density and impurity content of H-Mode discharges. The transient heat losses caused by them are of particular concern for ITER due to the large transient power loads expected on the divertor tiles. Although their existence is known since many years, their physics is not well understood yet, and search for ELM precursor activity which could bring light into its mechanism and control possibilities has been performed in many devices. Type-I ELM precursor modes were observed in JET through multiple diagnostics and studied in detail.