Clearly it is possible to use self-replicating microscopic things (cells) to produce macroscopic objects.  Life does indeed prove this.<p>But, you know, it takes billions-of-years evolved plantlife about 20 years to produce a simple structural element able to support maybe a thousand lbs and 20 feet long (ie, to grow a tree).  We notably do not see anything in nature that does &quot;molecular assembly&quot; from microscopic cells to differentiated macroscopic objects in a time-scale of less than months.