On 10th August 2023, Dr. Flora Lau completed a conference presentation organized by Oxford Nuffield College and UNICEF on researching hidden population. The theme of the conference is “Hard to reach: applied research methods with hidden, marginal and excluded populations”. She shared her research experiences with asylum seekers and ethnic minority cancer patients in Hong Kong since 2016 and confessed the fundamental importance of accessing the target group and collecting information on one hand, and being and feeling engaged in the community on the other especially for ethnographers in order to avoid being manipulative. Researchers doing hidden population must be reminded of all ethical issues concerned.