A crucial yet unavailable component in high-performance photonic integrated circuits (ICs) and other chip-scale photonic systems is an on-chip light source that is efficient, economical, IC-compatible, and electronically addressable. In this talk, I will cover several types of on-chip sources, including III-V nanoLEDs and topologically protected microlasers, perovskite microlasers and luminescent hyperbolic metamaterials, and III-N spintronic THz emitters. I will also discuss emerging applications of these metamaterials and devices, such as photonic neuromorphic networks.