Vasculogenesis is de novo production of capillary meshwork during development.This process can be reproduced by a primary cell culture system.Recently, fibrin gel culture system is utilized to generate perfusable capillary network in microdevice.In this culture system, HUVECs were embed in fibrin gel and cultivated with human lung fibroblasts (LFs).Then, the cells were interconnected to form meshwork within 24 hours.To understand the pattern formation in this culture system, we use two classes of models to represent early and late phases of pattern formation.For early phase, we simply describe the process using rule-based model in which cells i and j are connected by a certain probability defined by distance between cells.In the late phase model, the boundary between cells and fibrin gel moves by constant speed V.With these simple assumptions, we can reproduce the observed pattern formation processes.