Thermal Platforms heat or cool your device-under-test via conduction.

The Aluminum plate itself is electrically-heated via heating rods embedded below the surface.
It is typically cryogenically-cooled via liquid N2 or liquid CO2 vaporizing inside the plate.
The heat/cool cycle is governed via an adjacent programmable controller.

Typical temperature range is -100 degC to +200 degC. Ramp rates are controllable from zero to tens of degreesC per minute.
The most popular (& least-expensive) plate sizes are 6.75" square and 11" square, but there are many smaller and larger sizes available.

Options include an insert pattern in the top face, adapter plates, see-thru covers, cryogenic hoses, etc.

Sigma Systems has been the dominant brand in the Thermal Platform market for many decades.
Originally manufactured in San Diego, these products are now made at the Mansfield, MA headquarters of inTEST Thermal Solutions.