Embryonic development depends on the precise regulation of gene expression by transcription factors (TFs), whose concentration changes rapidly in space and time as they lay out the adult body plan. A widespread assumption is that instantaneous TF input concentration dictates output mRNA production. However, recent studies in various organisms have challenged this readout mechanism by demonstrating that the frequency, derivative, and fold-change of TF concentration can also provide regulatory information. To put these different scenarios to test, it is necessary to manipulate the dynamics of the input TF at will. We established the optogenetic control of Bicoid activator concentration dynamics. Bicoid, one of the most widely studied transcription factors in development, was fused to the LEXY optogenetic tag and the mCitrine fluorescent protein using CRISPR/Cas9-mediated homologous recombination. Upon illumination with blue light, LEXY is activated, leading to the nuclear export of Bicoid molecules. By combining this optogenetic system with the MS2 system to measure transcriptional activity, we show that we can independently control and measure Bicoid concentration dynamics and its resulting effect on the transcription of a reporter gene. We utilized this tool to study how Bicoid concentration is read out in time by the hunchback P2 enhancer. Here, we present our progress towards understanding the temporal readout mechanism of TF concentration in development, with the ultimate objective of deriving theoretical models that predict output mRNA dynamics from knowledge of the input TF concentration.