High performance computer systems continue to increase in size and complexity. Tools that measure application performance in these environments must evolve and keep pace with the changes, taking advantage of new sources of performance data as they become available. PAPI (the Performance API) has provided platform and operating system independent access to CPU hardware performance counters for the last decade. Recent trends toward massively parallel multi-core systems present new challenges for the measurement of hardware performance information, which now not only comes from the CPU core itself, but also from sources scattered across the chip and system. The introduction of Component PAPI, or PAPI-C, allows multiple sources of performance data to be measured simultaneously via a common software interface. This talk explores the design of PAPI-C and the opportunities presented by performance components, as well as exploring future directions for the PAPI interface.