As X-rays may pass through matter, X-ray Fluorescence (XRF) allows the determination of layer thickness. Using micro-XRF on SEM, the layer analysis (thickness and composition) is rendered feasible with spatial resolution at the micrometer scale. Layer analysis is strongly based on quantification using atomic fundamental parameter (FP). It can be improved with the use of standard samples, so various types of layer systems can be investigated by FP, such as metallization on wafer, multi-metal pretreatment coatings and solar cells. When standards are available, they can be used to enhance the accuracy. But since FP does not require standards, novel layer systems in an R&D environment can also be tested. Layer structures, such as solar cells (Fig. 1), are important in numerous industries.