In their early stages of formation, the objects that will eventually become stars are small. They grow by gathering material from the surrounding cloud of gas. At least, that's what current theories tell us what happens. Due to the difficulty of resolving star systems during their formative years, most observations have been from later periods of their evolution, after the protostar has reached a substantial fraction of its final size and mass.
A new observation has revealed the youngest protostar yet observed. John J. Tobin and colleagues measured the properties of the newborn star and its environment, determining that it had only accreted about 20 percent of the matter surrounding it, and hasn't even begun nuclear fusion. Based on this, the protostar was likely no more than 300,000 years old at the time of observation, with the distinct possibility that it was even younger.
Ars Technica: Astronomers discover youngest protostar yet observed, Matthew Francis