A detailed understanding of dynamical processes in molecules requires dedicated and controlled experiments in close interplay with high level theory. State-of-the-art measurements employ excitation pulses for the start of the reaction that are tuned into a transition that leads to the desired molecular level. We have developed optical parametric sources that can be tuned gap-free from 200 nm to beyond 5 µm with sub-50 fs pulse duration. For probing of the temporal evolution extremely stable white light pulses with a spectrum ranging from 280 nm to 750 nm and a controlled delay are used. This allows to utilize the proper spectral windows that render unambiguous information. The recent demonstration of continua ranging well into the infrared will soon allow us to expand the observation range to at least 1500 nm.

The capability of these methods will be demonstrate with examples from photophysical and photochemical processes. We do not only determine the reaction rates, but more importantly we can uniquely decipher the reaction mechanisms. Many surprises are found in systems where classical understanding seemed to be well established.