The origin of life on Earth is still a hotly-debated topic. There are many different theories on how life was kick-started, as well as various experiments underway attempting to understand the processes involved.
For example, a reverse engineering
approach can be used by stripping away cells until the simplest possible system is left. However, evolution has ultimately hampered our understanding of life's origins as it has washed away the traces of the first forms of life, making it impossible to retrace life's early steps. This means that even the simple systems left after the reverse engineering approach are still too complicated to bear a resemblance to the first forms of life.
Life must have started simply; it couldn't be created from a complicated group of molecules already working together. There had to a step prior to this in which these molecules themselves were created. Terrence Deacon, of the University of California Berkeley, outlined in a recent talk how this step could have taken place. [7 Theories on the Origin of Life (Countdown)]