It is spoken about a lot - how witnesses of UFOs claim they appear without rivets, seams, or signs of construction. Bob Lazar compared it to injection molding. But, how do you build something without parts and then place beings within it? 

We may have learned the technology either by example of examination of actually downed craft. 

MIT and other institutions are revealing a concept of "kilobots" that are tiny robots that have the ability to be programmed for a collective goal - perhaps to create an airplane or form a house. They could self assemble like atoms to create the structure. Then, they can be programmed in specific ways. Perhaps, to allow for one individual to be allowed to go through the structure unharmed while others will hit a wall. 

There's implications for this swarming robots technology. First thing that comes to my mind are how to build a space ship without panels and seams. 

The other thing that comes to mind is Skinwalker Ranch. There, a UAP is seen going through a mesa and out the other side. The same thing is reported about UAPs that can move in transmedium from sky to water, without any resistance at all. 

Let's go a bit further with this concept. If a UAP is made of this technology, it would be completely ignorant of things like gravity and solid objects. If the ship easily entered the mesa and came out the other side, the occupants inside were protected by the tech that surrounds them, the ship. 

The bigger question is, did the government and its aerotech companies associated with it, come to this concept from studying the downed UAPs? 

Or, did this technology happen to lead us closer to their levels of tech understanding and therefore making their more frequent visits makes sense as they realize we are about to join the galactic community? This would be rather like excited parents watching the toddler to witness first steps. 

A quick online search for swarming robots will really shed light into the future.