This article examines the research value of the administrative records of the Governmental Control and Optation Commission of the Republic of Estonia. The Commission was responsible for granting Estonian citizenship to ethnic Estonians who lived in Soviet Russia after the collapse of the Russian Empire and wished to return to their historical homeland. It also organized their resettlement to Estonia in 1920–1922. The Commission’s work helped regulate the migration flow that emerged in the context of early Soviet legislation on the right of peoples to self-determination, the Treaty of Tartu between the RSFSR and Estonia, signed in February 1920, the Estonian Declaration of Independence, and the 1918 Citizenship Law of the Republic of Estonia. Drawing on the case of Estonian emigration in the early 1920s, the article shows how administrative records preserved in the National Archives of Estonia can be used to study diaspora and migration processes. Most of these materials have not previously been introduced into scholarly circulation. Their identification and systematization make it possible to reconstruct the migration process from the submission of citizenship applications to resettlement in Estonia on Petroevac trains. The microhistorical approach adopted in the article makes it possible to explore the everyday lives and individual trajectories of Estonian optants, whose acquisition of citizenship depended on their return to the territory of the newly established Estonian state. The authors argue that the records of the Governmental Control and Optation Commission allow researchers to distinguish two main stages of the process: a preparatory stage, in which potential migrants — Estonians opting for citizenship — were identified, and a subsequent stage involving their actual relocation. The Commission’s documentation thus offers a multifaceted perspective on this migration process, moving beyond a narrowly political or historical approach and placing it within a broader interdisciplinary framework.