The evolution of ultrashort-pulse laser physics and technology is culminating at the start of this new millennium with the generation of intense few-cycle light pulses with controlled envelope. A lot of new exciting phenomena were experimentally observed as: high (many hundreds!) harmonic generation, attosecond x-ray pulse generation, x-ray lasing, molecular dissociation and other. The aim of this review report is to discuss the impact of these pulses on high-field physics. Particular emphasis is placed on high-order harmonic emission and single subfemtosecond extreme ultraviolet/x-ray pulse generation. They represent the core of a newly emerging field of science - attosecond physics. Technological development is based on the ever increasing control over laser pulses. Pulses with durations of a few tens of femtoseconds and intensities around 1014 W/cm2 are routinely available today. However, pulses with durations near the limit of a single field oscillation (less than 5 fs) can presently be generated at several laboratories only. The mode-locked Ti:Sapphire oscillator followed by chirped pulse amplification and optical compression represents the base of such technology. Practical scheme of such devices are analised. Intensity of 1014 W/cm2 corresponds to laser field of several 108 V/cm comparable in strength to the electric field of the atom. The value of 108 V/cm is crucial for light-matter interaction phenomena. Nonlinear interactions taking place under lower values can be well described by a perturbative approach, and hence we refer to this parameter range as the regime of perturbative nonlinear optics. One of the conditions to reach such intense light fields is the applications of ultrashort pulses, otherwise optical damage occurs. The specific of perturbative nonlinear optics is that third and next orders of nonlinear responses are much smaller than the second order. So, only second order processes can be effectively generated. If the electric-field strength becomes comparable to (or higher than) the binding atomic Coulomb field experienced by the outer-shell electrons, an electron can escape with a substantial probability from its bound state (via tunnelling or above-barrier detachment) before the laser electric field reverses its sign. This phenomenon has been first analysed by Keldysh (1965): Tunnelling occurs when the cycle-averaged kinetic energy of the electron exceeds the binding energy Wb. Such processes are referred now to the strong-field regime of nonlinear optics, or extreme nonlinear optics. Light is able to ionize atoms within a single wave cycle. In the most experiments jet of inert gas (Ar, Ne, Xe) are used. Extreme UV or soft X-ray generation from solid state targhets are experimentally obtained also. More over, the electrons created from ionised atoms can be accelerated up to relativistic speeds at laser intensities around 1018 W/cm2, obtained with few-millijouls pulse energy only. Thus, high speed ionised particles (relativistic plasama) can be obtained in laboratory conditions by table-top experimental setup. In conclusion, one can see that intense one cycle light generation is a great challenge to the research community, but also has the potential of a significant impact on numerous fields. Microscopic motion of electrons plays a key role in advancing the technology of compact X-ray sources. Significant response of electrons to light oscillations on the time scale of the laser cycle represents the bases for lightwave electronics. The gaps between photonics and electronics are bridged by the microscopic motion of electrons in atoms, molecules, and nanoscale structures. Vice versa, the electronic motion inside atoms is behind the emission of visible, ultraviolet, and x-ray light.