Virtual Reality immersive environments are becoming more popular and of less cost, hence, VR labs are becoming a main part in any research that depends on visualization. This introduced the need to port many 3D desktop visualization applications to VR. Porting application GUIs can be a problem since original GUIs are 2D by nature and using them directly can obscure a large area of 3D viewport and spoil the immersive experience. On the other hand, rewriting a 3D GUI can be a time consuming and tedious task. In this work, we introduce a technique to embed 2D GUIs into 3D Virtual Environments .This API, developed by VISTA team, uses existing 2D GUIs that can be immersed into the VE allowing rapid GUI development for VR applications. It can also be used for porting 3D desktop applications without rewriting the GUI code. Further, it enables embedding many window-based desktop applications into the VE, creating rich VEs where users can work with multiple applications simultaneously.