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The early phases of solar-type star formation is taking place within cold dense cores. To assess if this holds for high-mass stars as well is a pending problem because only little observational evidence for massive cores in a pre-stellar state has been found. Our search for such objects has used the ISOSS 170 um survey and established a sample of potentially massive star-forming regions that exhibit very low average dust temperatures. Detailed studies reveal a population of cold clumps (12 K to 21 K) with masses of 2 to 170 M_sun and sizes of 0.1 to 0.4 pc. Despite the low temperatures we detect young stellar objects associated with the clumps implying active star formation. Interferometric maps of the regions ISOSS J23053+5953 and J18364-0221 identify three cores of < 10000 AU sizes and masses of ca. 20 M_sun that appear to collapse. While their emission at 24 um is very low, we discover molecular outflows which have been launched early in the collapse. In case these objects develop high-mass stars they are among the youngest known examples. They are on the target list of our HERSCHEL Key Program The earliest phases of star formation to establish precise local dust temperatures which are crucial to derive core masses.
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