The giant molecular cloud complex SgrB2 is the most massive region with ongoing star formation in the Galaxy. It is located at a projected distance of about 100 pc along the plane to the Galactic center and at 8.5 kpc from the Sun. The whole complex contains a total gas mass of 10^7 Msun, with the main sites of active star formation corresponding to the hot molecular cores SgrB2-N and SgrB2-M that are located at the center of the complex. They contain more than 50 high-mass stars with spectral types ranging from O5 to B0, and constitute one of the best laboratories for the search of new chemical species in the Universe. We have conducted a high-spatial resolution, spectral line survey of the two hot cores SgrB2-M and SgrB2-N with ALMA. Despite their similar masses (3–7x10^4 Msun) and luminosities (1-6x10^5 Lsun), the ALMA observations reveal clear differences between the two objects. A study of the continuum emission reveals a clearly fragmented structure in SgrB2-M, while SgrB2-N remains monolithic and contains one of the, probably, most massive, not fragmented condensations in the Galaxy. Furthermore, SgrB2-M and SgrB2-N have a very different chemical composition, with M being rich in sulphur-bearing molecules and N in organics. The observational results are compared with 3D radiative transfer models. Here we present the first results of the ALMA project as well as some new tools to characterise the continuum emission in line-rich sources, as well as the spectral line properties.