Nucleon is a Minecraft modpack for 1.12.2 that is currently being developed. It is a skyblock modpack that aims to subvert your expectations.
Nucleon has none of the typical skyblock mods like Ex Nihilio, Sky Resources or Sky Orchards and no resource generation mods like Mystical Agriculture, Fluid Cows or Chickens. It uses its own custom mod, Energy's Matter. Every basic resource has its own complex processing chain. However, after you get 4 to 8 of a given resource, you are able to duplicate it using the custom machines in Energy's Matter.
The most prominent feature of Nucleon is its focus on intertwining the mods. Every mod is split up into multiple parts based on your technology stage. Even after "completing" the first segment of that mod, you will need to progress in other mods before being able to use its more advanced mechanics or powerful features. Within each technology stage, there are many points at which the different mods in that stage will require progress from another mod in that stage for progression. Unlike conventional "expert" packs, which gate a mod and then, after have almost no connections to other mods, Nucleon mods will remain intertwined long after beginning them. A more detailed technology tree can be found here.
Even from the beginning of the pack, you will be using advanced crafting techniques such as the Molecular Assembler Device for many of your recipes. These crafting mechanics are primarily used for machines and multiblocks, and not for crafting materials to alleviate the increased complexity of automating such recipes.
Nucleon makes heavy use of ContentTweaker and Modular Machinery to add its own custom content to the game.