Network functional combination is a promising direction in enhancing Internet adaptability. It decomposes the current layered network into fine-grained building blocks and combines them on demand. However, what legacy functions should be decomposed and how to combine them in an optimal way are unclear. We propose a novel adaptive architecture called reconstructive network architecture (RECON) based on the principles of the Complex Adaptive System. This study has three main contributions. First, RECON decomposes functions of the protocol stack at layers 3 and 4 into fine-grained building blocks, called atomic capabilities to open the network core functions unlike existing solutions. Second, RECON can customize different service chains on demand by combining atomic capabilities in an optimal way. We formulate the atomic capability combination into a nonlinear integer optimization problem with the proposed algorithm to reach an appropriate tradeoff between the optimal solution and computation cost. Finally, we implement a proof-of-concept for RECON in the network node. Results are corroborated by several numerical simulations.