The last decade has acknowledged the emergence of a new paradigm for building large-scale distributed systems: the microservice architecture. As opposed to the classical tightly coupled monolith architectures, this paradigm promotes small loosely coupled autonomous services, so called microservices. Such software services are to be small to encapsulate a well-defined functionality and thus facilitate bug isolation and maintenance. They should be loosely coupled to support independent software updates. Finally, they need to be autonomous to enable independent delivery to production. Adopting microservices becomes a general trend and experts predict that "by 2022, 90% of all new apps will feature microservices architectures". Among companies working around microservices are infrastructure providers, including GAFAM and EOLAS, major IT players, including Netflix and Uber, but also telco operators, including Orange. They all build on the container technology to facilitate functionality encapsulation, dependency isolation and standalone deployment, as required by microservices. However, the current used orchestration solutions (e.g., Kubernetes) struggle with the scale and the heterogeneity of microservices and fail to fix the performance problems fast enough. The challenge addressed by the SCALER project is to optimize the scaling of microservice-based networked services while satisfying their stringent IT and telco requirements. The proposal targets three research aspects, namely automatic microservice characterization, identification of microservice interaction patterns and microservice smart-scaling. SCALER brings together two academical and two industrial partners, namely LIG ERODS, INRIA Spirals, Orange Innovation and EOLAS B&D.