And that means it must be a solid at this particular temperature and this particular pressure. Now, if we keep the pressure the same and, say, increase our temperature to say, this point, well, then we have to draw the line all the way here. And then the section will be here at this pressure. At this temperature, it will be in a gas phase. Now, the lines or boundaries represent or signify dynamic equilibrium between two or more phases. For example, suppose I'm on this boundary and on this line well, at this line, the rate at which the soil becomes a liquid is the same as the rate at which the liquid becomes a solid.