45Gut microbiome are studied primarily using fecal samples in humans and we gained 46 vital knowledge of compositional and functional capacities of gastro-intestinal 47 microbial communities. Yet, fecal materials limit our ability to investigate microbial 48 dynamics in different locations along GI-tract (in situ), nor in finer temporal scales as 49 they are infrequent. With a technology developed originally for fecal material 50 transplantation, colonic transendoscopic enteral tubing, we were able to sample 51 ileocecal microbiome twice daily, and carried out metagenomic as well as 52 metatranscriptomic analyses. Ileocecal and fecal microbiome are similar in 53 metagenomic profiling, yet their active genes (in metatranscriptomes) are highly 54 distinct. Both were perturbed after laxatives and then became more similar to 55 microbiome prior to treatment, demonstrating resilience as an innate property of gut 56 microbiome. Ileocecal microbiome transcriptomes sampled during day and night 57 revealed diurnal rhythmes exist in certain bacterial species and functional pathways, in 58 particular those related to short-chain fatty acid production. Lastly, metabolomic 59 analysis in fecal and urine samples mirrored the perturbance and recovery in gut 60 microbiome, indicating crucial contribution of gut microbiome to many of the key 61 metabolites involved in host health. Our study provides interesting novel insights into 62 human gut microbiome, and demonstrates the inner resilience, diurnal rhythmes and 63 potential consequences to the host. 64 65 66 (Figure 1, Figure S1). Yet those microbial species do not always occupy the majority 131 in RNA reads, rather, species Ruminococcus torques, Methanobrevibacter, 132