15A recurrent challenge in biology is the development of predictive quantitative models 16 because most molecular and cellular parameters have unknown values and realistic models 17 are analytically intractable. While the dynamics of the system can be analyzed via 18 computer simulations, substantial computational resources are often required given 19uncertain parameter values resulting in large numbers of parameter combinations, 20 especially when realistic biological features are included. Simulation alone also often does 21 not yield the kinds of intuitive insights from analytical solutions. Here we introduce a 22A major goal of systems biology is to develop quantitative models to predict the behavior 36 of biological systems (1, 2). However, most realistic molecular and cellular models have a 37 large number of parameters (e.g., reaction rates, cellular proliferation rates, extent of 38 physical interactions among cells or molecules), whose values remain unknown and are 39 often challenging to measure or infer quantitatively (3, 4). While some biological 40 phenotypes are robust to parameter variations (5), most are "tunable" by parameters (6). 41Therefore, analyzing the behavior of a system over the entire plausible space of parameters 42 is needed to study the phenotypic range of a biological system and its parameter-phenotype 43 relationships (7-9). A case in point concerns a contemporary problem in single cell biology: 44Despite the increasing availability of single-cell gene expression data enabled by rapid 45 technological advances (10), an important unanswered question is how cell-to-cell 46 expression variation and gene-gene correlation among single cells are regulated by the 47 computational resources are required to analyze the parameter space, given the large 59 uncertainty in parameter values and the complex correlation structure among parameters. 60Plus, simulation analysis alone often does not automatically yield intuitive understanding. 61Here, we combine computational simulation of full-feature stochastic models and 62 machine learning (ML) to develop a framework, called MAchine learning of Parameter-63Phenotype Analysis (MAPPA), for constructing, exploring, and analyzing the mapping 64 between parameters and quantitative phenotypes of a stochastic dynamical system (Figures 65 1A and S1; Supplementary text). Our goal is to take advantage of the large amounts of data 66that can be generated from bottom-up, mechanistic computational simulation of dynamical 67 systems and the ability of modern machine learning approaches to "compress" such data 68 to generate computationally efficient and interpretable models. MAPPA thus builds 69 efficient, predictive, and interpretable ML models that capture the nonlinear mapping 70 between parameter and phenotypic spaces (parameter-phenotype maps). The ML models 71 can be viewed as "phenomenological" solutions of the SME that can predict the system's 72 quantitative behavior from parameter combinations, thus bypassing computationally 73 expensive simulatio...