The 2020 edition of the Exposome Boot Camp run by the Columbia University Mailman School of Public Health will be held online due to the current world situation. Further details are on the website. https://www.publichealth.columbia.edu/research/precision-prevention/exposome-boot-camp-measuring-exposures-omic-scale This record contains the slides for the MetFrag demonstration for the 2020 edition, plus the accompanying exercises and files needed. The organisers have agreed that this material can be made publicly available for others to use - enjoy! A huge thanks to my group and all collaborators throughout the years that have helped make this work possible.