Enterprise applications are migrating to cloud as mutli-tenant SaaS. To empower businesses with highly customizable SaaS, software vendors need a novel approach for customizing SaaS in mutli-tenant context that still benefits from moving to cloud. In this initial industrial experience report, we present our design and experimental findings towards a novel and cloud-native architecture of customizing multi-tenant SaaS by microservices. The report clarifies the key concepts related to the problem of multi-tenant customization, nd describes a design with a reference architecture and high-level principles. An experimental use case to customize an open source web-based shopping application demonstrates that a microservice-based approach is feasible to meet the general customization requirements, and achieves a balance between isolation, assimilation and economy of scale.