I have a cyborg head blend file that is in a collection, composed of many meshes. I need to repeat this head in equidistant rows and columns. The duplicated heads must be linked copies so that if I adjust the color of the eyes for instance, they will all change. Can anyone help please? Thank you in advance.
1 - create an empty
2 - Go to object settings > Instancing and select “collection” and select the colection that is the cyborg head.
3 - Duplicate the empty a load of times
4 - If you need to hide the original cyborg head, move it’ collection into a collection called “hid”, and hide the collection “hid” (you can call the collection anything you like, but “hid” explains what it is and has only 3 letters)
Thank you yogyog! That’s what I was looking for! 
I forgot about Instancing. I’m such a newb 
Depending on how many it are it might make sense to use particles.
If there are going to be several thousand of heads the above mentioned method will probably be slow.
Or you can use duplifaces on the empty in my last example.
If you duplicate the empties you create objects. Blender starts getting slow at around 4000 objects and nearly unusable at around 8000.
You can use a mesh and use dupliverts or duplifaces but with particles you would have more options to add some variance (color and other shader options, rotation, size and so on).