Communication is one of the most important human activities. Its original goal was sharing information among people. But sometimes information is intended only for certain persons and it is not acceptable to transfer it using common ways. Therefore people have been developing safe (private) forms of communication for ages. Absolute privacy of our information had never been guaranteed until scientists showed, during the last decades of the 20th century, that communication without eavesdropping is possible. There exist a number of useful applications of quantum mechanics and quantum cryptography (the name for a part of quantum theory focused on the studying of safe communication) is one of them. In our article we explain the basic principles of quantum cryptography with attention paid to the first known quantum protocol BB84. Theoretical and experimental progress in the field of quantum cryptography during the last few years will be briefly discussed as well.