Pressure is extremely efficient in tuning the interactions in soft material such as the molecular ones. As a result, important changes of the structural, dynamical and chemical properties can be induced even in relatively low pressure regimes. After a general introduction directed to outline the importance of high pressure in nature and the instruments necessary to create high pressure conditions in laboratory, the attention will be focused on two different, although connected, problems: the chemical transformations of simple model systems under pressure and recent challenging experiments directed to understand the dynamics of ultrafast processes driven by pressure. As the reactivity is concerned, the complex interplay of structural properties, lattice dynamical processes and electronic arrangement will be discussed through several examples pointing to the importance of disentangling the effects of pressure, temperature and laser (or x-ray) radiation on the reaction activation to understand the reactivity at the molecular level. The second part of part will be devoted to the application of ultrafast spectroscopic techniques to samples compressed in high-pressure devices. These experiments are extremely challenging having so far precluded the studies of ultrafast dynamics (reaction intermediates, phase changes, structural rearrangements) driven by pressure. Recent results on the dynamics of liquid water, water solutions and ices demonstrate the feasibility and potentiality of this approach in monitoring non equilibrium states under high pressure conditions.