With climate change the occurrence of extreme weather events will increase, making stress resilience an essential trait for future crop breeding. Whilst we have a good understanding of the effect of single stress factors on photosynthesis, there is a knowledge gap on how combined stresses affect the photosynthesis. The combination of drought and heat is of special interest since they have opposing effects on stomatal regulation. Chlorophyll fluorescence can be applied in medium and high-throughput phenotyping and Fv/Fm can identify heat tolerant and sensitive genotypes, while low-throughput gas exchange can establish the mechanistic relationships that relate to harvest yield during stress. Most measurement of photosynthesis is done at steady state and saturating light after application of a single stress. Recent results indicate the importance of the way photosynthesis responds to combined stresses and fluctuating light. This chapter discusses how to perform analyses reflecting these more complex conditions.