In the frame of long-wavelength Heisenberg model, a simple magnonic mono-mode circuit is designed to obtain transmission stop (pass) bands where the propagation of spin waves is forbidden (allowed). This simple device is composed of an infinite one-dimensional mono-mode waveguide along which side resonators are grafted. These circuits are usually mono-mode when the lateral dimensions of the conducting wires are small as compared with the magnon wavelength. Their production utilizes the most advanced surface technologies and represents one of the most important challenges for the next decade. In all these circuits, the interfaces between the different wires out of which the circuits are made of, play a fundamental role. All such circuits exhibit a variety of interference effects in their transport properties. Emphasis in this chapter is placed on the network creations called magnonic crystals, which include stubs or resonators interconnecting branched networks. In other words, a fundamental understanding of nanoscale materials has become an important challenge for any technical applications. In addition to magnonic crystals, we show that simple structures made of a few stubs along the waveguide may exhibit Fano and magnetic induced transparency resonances. Results for the transmission and reflection properties of such circuits (nanometric networks) are discussed as a function of the frequency of the excitations and the physical or geometrical properties of the circuits. These magnonic circuits can be used for the design of integrated devices such as narrow-frequency optical or microwave filters, high-speed switches, multiplexers, storage devices, etc.