European Researchers' Night is a popular and highly anticipated annual event in Estonia and it has been celebrated here since 2005. The main purpose of the European Researchers' Night in Estonia (RNEst) is to highlight the most recent and important accomplishments of researchers and encourage young people to choose careers in research, engineering and STEM-related areas (by introducing these professions through numerous entertaining hands-on activities). The main topics of the RNEst21 events will be drawn under the theme of 'Food For Thought' which allows focusing on various disciplines (such as engineering, chemistry, biology, sociology, history or psychology). Events of the European Researchers' Night in Estonia cover the whole country with science-related, fun and engaging events offering a colourful programme for various target groups (including families, students, young adults and seniors) in almost every county in the country. RNEst21 activities allow the public at large to meet researchers, to have discussions with them, ask questions and find out what they do for society. Events include hands-on experiments, science theatre shows, learning activities for children, guided visits in research labs and facilities, science quizzes, TV and radio programmes, stand up science shows and more. Also, pre-events such as preparing researchers for engaging with the public (e.g. summer schools) will be organized. Estonia has celebrated European Researchers' Night for 15 years and each year more than 200 scientists are involved with the events that take place in almost every county of the country. Each year around 60 schools and 80 other educational institutions open their doors and offer programmes for science enthusiasts and the public at large. To stress the importance of collaboration in the pan-European Researchers' Night, joint events are going to take place in cooperation with other Researchers' Night organisers from across Europe.