When examining a monthly bank account statement, it is not only the number below the bottom line that matters. Whether that number has a minus or plus in front of it is crucial. For many technical problems, the sign matters as well. In circuits, we can change the sign by means of phase shifters. Moreover, by using phase shifters, intermediate states between the signs (including complex values) can be set in circuits. Hence, phase shifters play an important role in electrical engineering. Unfortunately, this article does not give direct insights to change the sign of your bank statement. However, it aims to give a comprehensive overview of tunable phase shifters for radio frequency (RF) applications including cookbooklike design guidelines and performance comparisons. The focus of this article is put on phase shifters fully integrated in a chip.