Two smectic A phases from two different materials have been used. One of them belongs to the cyano-biphenyl series: 8CB (4-n-octyl-4’-cyanobiphenyl). The second one, called TBDA (terephthalylidene-bis-4-n-decylaniline) also possesses a smectic A phase. 8CB is a nematogenic compound whereas TBDA does not possess any nematic phase; TBDA transits directly into the smectic A phase from the isotropic phase when the temperature is decreased (TI/SmA∼190∘C). Optical measurements were performed with a polarizing microscope (Olympus CX60) coupled to a digital camera which provides images on a computer via an acquisition card. Image Pro Plus (IPP) software permits the recording of the photographs. The temperature control is performed using a Hot Stage HS-2 from Instec which provides a thermo-stabilization accuracy better than ±0.01∘ C and a temperature change at a controlled rate, which can be as low as 0.005∘ C/min. Some droplets of liquid crystal have been deposited between two untreated slides. The liquid crystal is surrounded by a glycerol matrix.