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A major breakthrough in the expansion of properties of polyolefins was the development of single-site organometallic catalysts that allows living polymerization and synthesis of olefin based block-copolymers (OBC). The drawback of living polymerization consists in that it entails growth of just one polymer chain/metal center. To reduce catalyst consumption, coordinative chain transfer polymerization techniques were implemented. Such technique involves the use of a single transition metal catalyst and a main group metal alkyl acting as chain transfer agent (CTA). The transfer of the growing chains from the catalyst to the CTA enables growth of multiple chains/active center, saving atom economy and allowing for the synthesis of BCP starting from the resultant polymers. Recently, using high throughput tools, the chain shuttling polymerization was discovered as an alternative and efficient way to produce OBC in a single step. In particular, ethylene/1-octene multi block copolymers (EOBC) were synthesized by the Dow Chemical Company (trade name INFUSE) using a couple of organometallic catalysts and a CTA via a reversible chain transfer mechanism. EOBCs are thermoplastic elastomers characterized by alternating crystallizable hard and amorphous blocks, with low and high octene concentration, respectively, and a statistical distribution in the block number and length/chain. Because of the chain microstructure, EOBCs with similar molecular characteristics show subtle differences in crystallization properties but remarkable different mechanical properties. A pathway to elucidate the intricate chain microstructure of EOBCs, and the role played by the chain microstructure on their properties are presented.