The major chnallenges faced by cryptocurrency or blockchain today is the horizontal scalability without compromizing security. There have been efforts to overcome the issue of scalability. One approach is to split transactions through different blockchains like bitcoin, etherium, litecoin etc but this would mean lower transacational demand in each blcokchain and lower hash power. This would make someone gain enough hash power to make a double spend attack.
The other approach to scalability issue is lightning network. The idea behind this is to defer frequent transactions among fixed group of parties until the parties are finalized with all the transactions. This however would centralize the payment process and go against the core value of blockchain which is decentralization. Also, when there are already so many players operating in centralized space, do we really to create more centralized entities.
The third and the most attractive solution to scalability is sharding which means partitioning large amount of data into small parts. This solution has been adopted by popular blockchain comapnies like Etherium.
However to implement sharding in full fledge by Ethereum would take years and comes with so many challenges. And considering the increasing transactions cost over Ethereum network due to more number of ICOs launched under the in the network and more and more companies adopting the network for games and other purpose.
The primary requirement for blockchain to succeed is to increase TPS. Currently it's way below what centralized payment system like VISA can process which is around 55K TPS.
This is where Quarkchain stands out with its promise of delivering 100,000 TPS overtime without compromizing on security or decentralization.
This is one of the most promising ICO in recent times which is committed to deliver efficiency without compromizing on secruity.