A majority of existing research in large language models and generative AI systems focuses on scaling and engineering. In this talk, I argue that we need a principled understanding of the science of generative AI, in particular, to understand the reasoning ability of large language models. First, I present a Bayesian latent variable approach to enhancing in-context learning in large language models (LLMs) through optimal demonstration selection, demonstrating substantial improvements across various text classification tasks. Second, I argue that modern generative AI systems must be modular and collaborative to solve complex reasoning problems. I will introduce Logic-LM, a locally grounded neuro-symbolic framework that synergizes LLMs with symbolic solvers, significantly boosting logical problem-solving abilities. We will also briefly elaborate on how to build neuro-symbolic solutions to improve the compositionality in text-to-image systems. Our observations indicate that the future of generative AI is modular and collaborative, as opposed to a single-model system.