What made this tiny honeycomb-like structure?
Many insects lay eggs in tight clusters; because of the shape of the eggs (like honeycomb cells themselves), the cluster looks a bit like a honeycomb.  If you had a high quality macro shot, the eggs might be easier to identify definitively.

Newly hatched Beet Armyworms:



Wheel Bug (Arilus cristatus) Eggs:




  Wheel bugs are common in eastern North America, but are confirmed to occupy areas of Mexico and Guatemala.


With wheel bug for size:



My guess is that you found a cluster of Wheel Bug eggs.


  Females lay eggs at a low elevation on trees, bushes, twigs, and other objects.[5] Secreted glue serves as an adhesive which maintains the cluster formation of the eggs. - Wikipedia