Nano-analytical techniques and instruments providing both excellent spatial resolution and high-sensitivity chemical information are of extreme importance in materials science and life sciences for investigations at the nanoscale.In the past 3 years, the Zeiss ORION Helium Ion Microscope (HIM) has emerged as an instrument of choice for sub-nm microscopy and nanofabrication. The unique combination between probing the sample with (light) ions and detecting emitted electrons confers unique capabilities to the HIM, including high contrast imaging, high depth of field and direct imaging of insulating samples. To add capabilities for chemical analysis, the CRP-GL investigated within the CORE project C10/MS/801311 “He-SIMS” the feasibility of implementing secondary ion mass spectrometry (SIMS) on the HIM by studying and optimising detection limits and achievable lateral resolution. We demonstrated detection limits varying from 10-3 to 10-6 for a lateral resolution of 10 nm and 100 nm, respectively. Encouraged by these excellent results, the CRP-GL was mandated by Zeiss to develop a complete SIMS system dedicated to the HIM. This SIMS system, which consists of ion extraction optics and a compact high-performance mass spectrometer, was successfully tested by the CRP-GL on a HIM at the Zeiss R&D facilities in Peabody (USA) in April 2014. The worldwide first HIM with integrated SIMS will be installed in the coming months at the CRP-GL in the framework of the collaboration between the CRP-GL and Zeiss. The CRP-GL will then be equipped with a unique nano-analytical tool, which will become a commercial product in 2015/2016.This CORE proposal focusses on correlative microscopy performed on the HIM, i.e. the in-situ combination of high-resolution microscopy (detecting electrons) and high-sensitivity chemical mapping (detecting ions) using the same probe consisting of He+ or Ne+ ions. The project will deal with three brick stones to reach the overall objective of HIM correlative microscopy: investigation of fundamental aspects of combined ion and electron detection under the irradiation by a light ion beam, development of correlative workflows and applications.