mSATA
Direct Answer
mSATA (Mini-SATA) packed a SATA interface into the same physical card size as Mini PCIe, standardized in 2011 -- but despite sharing its connector and outline with Mini PCIe, it's electrically incompatible, carrying SATA signal lines instead of PCIe lines. M.2 has now largely superseded it.
Source: SATA-IO, SATA revision 3.1 (July 2011)
Specs
| Dimensions | ~30 x 51mm (Mini PCIe card size) |
| Interface | SATA |
| Standardized | July 2011 (SATA revision 3.1) |
| Status | Largely superseded by M.2 |
Same Connector, Different Signal
mSATA was announced by SATA-IO in September 2009 and formally standardized in SATA revision 3.1 in July 2011. It reuses the exact physical connector and card outline of the Mini PCIe expansion card standard -- same size, same edge connector -- but the two are not interchangeable: mSATA carries SATA transmit/receive signal lines to a SATA host controller, while Mini PCIe carries PCI Express lines to a PCIe host controller. Plugging one into the wrong kind of slot simply won't work.
M.2, introduced in 2013, offered a smaller and far more flexible physical specification along with support for faster PCIe/NVMe signaling that mSATA's SATA-only design couldn't match, and new laptop and motherboard designs shifted to M.2 within a few years of its introduction. mSATA drives and slots are now largely a legacy format, found mainly in older laptops and some embedded systems.