From the very moment of the formation of the modern Bulgarian state in 1878, the Bulgarian society and the state institutions had to face the problem of balancing between the accommodation of ethnic, religious and cultural diversity in the country and the aspiration for building a unitary nation-state. For more than a century (until 1989), Bulgarian legislation practically ignored the existence of different minority groups in the country and did not explicitly protect their rights. The process of changing the legislation to recognize the diversity and multiculturalism in the Bulgarian society and to protect the rights of minorities has started only after 1989, as an inseparable part of the democratisation of Bulgaria and its aspiration to join the EU. In addition to the legal recognition, different ethnic and religious groups were also "discovered" by the scholars from various fields in social sciences. The avalanche of studies dedicated to the ethno-cultural situation in Bulgaria followed soon, including the first sociological studies about the levels of tolerance and mechanisms for coexistence of different communities. The interdisciplinary research "Relations of Compatibility and Incompatibility between Christians and Muslims in Bulgaria" (1993-2000), conducted by historians, ethnologists, sociologists, political scientists, has brought forward the thesis that during the centuries of coexistence, the Bulgarian society has set up a sustainable mechanism for accepting otherness under the strictly observed unwritten rules. Both the majority Bulgarians and the minority groups accept otherness and are tolerant towards it on the level of everyday life, but the psychological division line is preserved and the boundaries of the formal parallel existence are seldom crossed. It was also noted that Bulgarians often have negative stereotypes about the "others" on the group level, but disregard them on the personal level and have no problem in accepting their neighbour, colleague or friend from a different ethnic or religious community.