  Soliton molecules are the manifestation of attractive and repulsive
interaction between optical pulses mediated by a nonlinear medium. However, the
formation and breakup of soliton molecules are difficult to observe due to the
transient nature of the process. Using the time stretch technique, we have been
able to track the real-time evolution of the bound state formation in a
femtosecond fiber laser and unveil different evolution paths towards a stable
bound state. A non-stationary Q-switched mode-locking regime consisting of
various transient solitons is observed in this transition period. We also
observe additional dynamics including soliton molecule vibrations, collision
and decay. Our findings uncover a diverse set of soliton dynamics in an optical
nonlinear system and provide valuable data for further theoretical studies.
