Kuarki – Traveller between wor(l)ds is a free-of-charge application for multilingual children from the age of five. It helps children develop their vocabulary and practice reading and writing. Children who use one language at home and another in school frequently suffer from gaps in their vocabulary in both of those languages. This app aims to help bridge these gaps, while also providing users with new knowledge in an interesting and fun way. The app also helps monolingual children who are learning a foreign language and would like to improve their reading comprehension capacities.