It is well known that most materials expand upon heating. However, there are some negative thermal expansion (NTE) materials, whose volume abnormally contracts upon heating, have been found in the past two decades [1-3]. The appearance of NTE materials provides one possibility to effectively control the thermal expansion of materials. For the development of NTE materials, one main challenge is the understanding the nature of NTE. The nature of NTE is sometime associated with some factors like phonon thermal vibration, magnetic ordering, valence state, electron orbit hybridization [1-4]. Most recently, a big family of NTE compounds has been found to have functional physical properties of magnetic, valence state, and ferroelectric [2-4]. We call these materials as functionalized NTE materials. The occurrence of such functionalized NTE materials gives a good strategy to control thermal expansion of those functional materials. In the present study, we have systematically studied the negative thermal expansion of PbTiO₃ (PT)-based materials which have been widely studied and applied as functional materials of piezoelectric, dielectric, non-volatile ferroelectric memory and so on. PT behaves a strong NTE over a wide temperature range of room temperature to its Tc (490 °C). The NTE control of PT-based ferroelectrics has been well established by various chemical modifications. Giant negative or zero thermal expansion has been found in PT-based perovskites. For example, the bulk coefficient of thermal expansion (CTE) of 0.5PbTiO₃-0.5(Bi_1-xLa_x)FeO₃ can be controlled from a_V = -4.06´10^-5/°C for the x = 0.0 to a_V = -0.71´10^-5/°C for the x = 0.2 by simply adjusting the composition of La. The adjustable CTE contains most NTE materials. A wide temperature zero thermal expansion has been found in some PT-based piezoelectrics (e.g. PT-Bi(Mg_0.5Ti_0.5)O₃) and multiferroic materials (e.g. PT-Bi(Ni_0.5Ti_0.5)O₃). The NTE is highly associated with the temperature behavior of spontaneous polarization, which has been evidenced by Raman spectroscopy and neutron powder diffraction. It means the NTE nature is highly associated with ferroelectricity. Recently, we proposed a new physical concept of spontaneous volume ferroelectrostriction (SVFS) for the possible nature of PT-based ferroelectrics. The NTE of ferroelectrics could be controlled by adjusting the SVFS through the chemical substitutions of cations with different ferroelectricity activity.