During the last decade, the advent of reliable lasers capable of producing pulses of light with duration of merely a few femtoseconds brought on a revolution not only in laser physics but in many other fields of science as well. The next step is to controllably produce pulses with duration in the attosecond regime. Attosecond technology is expected to lead to numerous applications in atomic and molecular physics and in material and surface science. The goal of this project is to improve the control of attosecond pulse generation, and to use this improved control to study coherent control of ionization dynamics in gases. In order to do this, an upgrade to the existing laser setup at Lund University is needed. Therefore, the first objective is to install a new state-of-the-art laser system for the production of attosecond pulses. The second objective is to use the new system to produce stable attosecond pulse trains where the number of pulses in the trains can be varied from about ten down to a single isolated pulse. Such control is beyond that what is currently available anywhere and is unique to this work. Very recently, using attosecond pulse trains centred below the ionization threshold of helium atoms, the Lund group observed a strong modulation of the ionization signal on an attosecond time scale. The depth of modulation depended on the separation between the attosecond pulses as well as on the number of the pulses in the pulse train. In the third objective of this proposal, the newly added control of the pulse trains will be used to study this very recent development further. The vision is to enable control of a broad range of ionization, excitation and dissociation processes in atoms, molecules and more complex systems by directly affecting the electronic motion on its attosecond time scale.