Precision Timing with the CMS MIP detector

The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the High-Luminosity LHC (HL-LHC). A new timing layer is designed to measure minimum ionizing particles (MIPs) with a time resolution of $\sim 30$ ps and a hermetic coverage up to a pseudo-rapidity of $|\eta| = 3$. This MIP Timing Detector(MTD) will consist of a central barrel region based on LYSO:Ce crystals read out with SiPMs and two end-caps instrumented with radiation-tolerant Low Gain Avalanche Diodes (LGADs). The precision time information from the MTD will reduce the effects of the high levels of pile-up expected at the HL-LHC, and will bring new and unique capabilities to the CMS detector. We present the current status and ongoing R&D of the MTD, including recent test beam results.