The document summarizes the emerging 3D printing industrial sector. It discusses key companies in the space like Ex One, Arcam, and ProtoLabs. It also addresses fundamental questions around the opportunities and challenges around industrial 3D printing of metals. Key points discussed include Arcam's leadership in 3D printed titanium hip implants, various countries' policy support for additive manufacturing research through organizations like America Makes, and predictions that the aerospace, automotive, and medical sectors could represent an $8.4 billion 3D printing market by 2025.