Sub-recent sediments in modern lakes are ideal to study early diagenetic processes with a combination of physical, chemical, and biological approaches. Current developments in the rapidly evolving field of geomicrobiology have allowed determining the role of microbes in these processes. Their distribution and diversity in marine sediments have been studied for some years. Comparable studies in the lacustrine realm, however, are quite scarce and mainly focused on the water column and/or very shallow sedi-ments. Thus, there is a need to determine the presence of living microbes in older lacustrine sediments. During the PASADO (Potrok Aike Maar Lake Sediment Archive Drilling Project) ICDP (International Continental Scientific Drilling Program) drilling, more than 500 meters of sedimentary cores were retrieved from this crater lake. A 100-m-long core was dedicated to a detailed geomicrobiological study. Here we report a complete in situ sampling procedure that aims to recover aseptic samples as well as determining active in situ biological activity