Crossmatching between Planck and Herschel data has revealed a number of candidate protoclusters with starbursting galaxies. These starbursting galaxies are believed to be progenitors of elliptical galaxies in the cores of today's massive galaxy clusters. In this thesis, multi-wavelength observations of the candidate starbursting protoclusters are shown and their physical properties are studied. Using SCUBA-2 observations, number counts, colours, photometric redshifts, star-formation rates (SFRs) and infrared luminosities of the 850 μm sources in the candidate protoclusters are estimated. More than 70% of the candidate protoclusters show overdensities of 850 μm sources compared with the field. Using the Very Large Array (VLA) 6 GHz observations, number counts, the far-infrared-radio correlation, morphologies and multiplicities of the radio sources are studied, in which tentative overdensities and AGNs are found. Using lens modelling, the source distribution of a lensed dusty star-forming galaxy (DSFG) is studied, revealing multiple components in its radio emission. Using the William Herschel Telescope (WHT) observations at optical/near-infrared, the 4000-Å breaks of the candidate member galaxies are identified, and their colours and photometric redshifts are estimated. Using millimetre spectroscopy at IRAM’s 30m Telescope, CO lines are detected for a starbursting galaxy in a candidate protocluster, and its physical properties are determined. The multiwavelength observations suggest that the candidate starbursting protoclusters lie at redshifts between 1 < z < 3, and their starbursting member galaxies are forming the majority of their stellar masses with SFR 1,000 solar-masses/yr, which is consistent with the peak of cosmic SFR-density (SFRD) at z ∼ 2. Future work and observations are expected to increase the sample of these extreme protoclusters and to understand the formation of galaxy and galaxy clusters.