This paper addresses the tragic events of September 11th, 2001. Provides a brief background on the philosophy of fire protection for high-rise buildings and the behavior of a fire within a compartment. It further describes the events and the particular scenario corresponding to the World Trade Center. No attempt is made of providing a description of what caused the collapse but the objective is more to illustrate the characteristics of the fire and highlight the possible uncertainties. The paper concludes with a list of lessons learned and questions yet to be answer but fundamentally, with a plea for a detailed analysis of this event and a subsequent plan for fire research. Understanding the mechanisms that led to the collapse of the World Trade Center will enable engineers to provide a safer environment for the users of similar and other types of buildings but also for the firemen that sacrifice their lives trying to save the lives of other people.