This chapter reviews the history of the revolution of nanotechnologies. The following topics are dealt with: from micro- to nanoelectronics; from the macroscopic to the nanoscopic world; from fundamentals to applications; a different physics; some examples; and various applications.

This chapter introduces the concept of an ideal nanocrystal, known as quantum dot, which will help explain the particular properties of nanosystems. Electronic-state density of atoms and molecules was discussed. The electronic energy levels are calculated by well-known methods of atomic and molecular physics, and quantum chemistry.

Within the integrated circuits of computers (which we can compare to 'artificial brains'), the data transmission between the different elementary elements the transistors is made by electrical impulse. It is interesting to note that within the human brain, and between the brain and the other different organs, transmission of information (a function fulfilled by the nervous system) is also based on electrical phenomena. The sending of information all along the system of nerve cells (neurons) is expressed by the propagation of a change in the electrical charge of the neurons' membrane. In this way, an electrical impulse goes through the nervous system to the organs. The electrical characteristics of nerve impulses were demonstrated two centuries ago, during a well-known experiment in which Volta placed two electrodes on frogs' legs and applied a voltage, in this way producing a movement. But it is only recently that the similarity between the transmission process of information in microelectronics systems and the nervous systems made researchers think of correlating transistors and neurons. This new scientific field, which relates microelectronics concepts and neurology, has been named neuroelectronics. The first point of interest in this approach (making transistors and neurons communicate with each other) is that an integrated circuit associated with a neuron (or a group of neurons) forms a sensor of the neurons' activity. Then, those systems would be able to monitor in vitro (within test tubes) the effect of new medicine on the nervous system, which will allow the reduction of in vivo (m-the-body) tests (on animals). The functioning of the human brain (a network of more than a hundred billion neurons) is far from being completely understood. To connect a neuron network to a microelectronic integrated circuit would allow the network to be observed while it was working and then to better understand the functioning of our brain; moreover, it would allow the use of this network to assist the computer in some tasks and calculations. This is the second major aspect of neuroelectronics. Finally, we can also imagine that an artificial microelectronics system could restore the communication in an area of the nervous system damaged after an ill ness or an accident. Those artificial neurons could be used for instance to repair spinal-cord injuries after some accidents. Of course, all those applications exist currently only in the speculative world of researchers, but the recent advances of neuroelectronics (a scientific field only ten years old) are promising. In the next sections these progresses will be briefly presented.

This chapter of the book about fabrication of nanostructures is subdivided into 8 parts. It discusses the situation of the problem; contribution of supramolecular chemistry; semiconducting nanoribbons; creation of nanostructures; patterning; hybrid techniques; writing via local probe microscopy; and design and development of molecular circuits.

In this chapter, the use of nanomagnets can resolve the issue of the selection of the zone to heat. In fact, in this case the dissipated heat is directly proportional to the concentration of magnetic nanocrystals. The heated zone will then be the reflection of the bioselectivity of the nanomagnets for the pathology to be treated. The frequency of the variation of the magnetic field used (between 100 and 300 kHz) will be a thousand times lower than the one used in a classical thermotherapy irradiation. This allows a heat dissipation caused exclusively by the interaction between magnetic field and magnetic nanocrystals.

In this appendix, only transmission electronic microscopy (TEM) will be discussed here. This technique represents a good choice for a tool for the study of nanomaterials, since it allows direct imaging of the samples. By observation of transversal sections, the linages can be obtained both at the surface and inside the sample. Structural characteristics, such as shape, size and distribution of nanometric precipitates, can in this way be obtained. Furthermore, the advent of high-resolution techniques has allowed us to examine samples down to the atomic scale, and consequently to have a precise idea of their nanostructure. To conclude, electronic microscopy techniques seem to have revolutionized and allowed the nanotechnologies domain to develop by their capacity to show the link between fabrication, structure and properties of nanomaterials, and all that down to the atomic scale.

The main application of the nuclear magnetic resonance (NMR) phenomenon is indisputably magnetic resonance imaging (MRI). This technique has been widely used for more than 15 years in the medical environment as a diagnosis tool. It allows the formation of contrasted anatomic images from the NMR signal of the protons of human bodies. The contrast is imposed by the protons' density of the tissues, by the longitudinal (T₁) and transverse (T₂) relaxation time, and by the acquisition parameter of the image.