The 3D Atlas users layers to allow you to explore the anatomical structures. Select the regional anatomy you're studying and use the interactive features to enhance the learning experience.
See the screenshot below that shows the regional anatomy options from 3D Atlas: Head & Neck; Spine, Shoulder & Arm; Forearm, Wrist & Hand; Thorax & Abdomen; Pelvis & Perineum; Hip & Thigh; Knee; Leg, Ankle, & Foot