How can I add Emission to the "Mortar" of a grid texture? I'm new at Blender, and so far I’ve made a simple grid:

That is how my grid looks right now, but I want the green part to emit light, I knew that emission would work well, but the input for that is a color, not a material.
Does anyone know how to make this?
If you generate your grid texture with a Brick Texture node, you can connect the Fac output to the Emission Strength input of a Principled BSDF:

Note the green glow cast on the small sphere.
If you want a more visible glow/glare around the grid itself, you could try adding some volumetric mist, or you could fake it with Bloom (in Eevee) or using a Glare node in compositing (in Cycles). Here’s an example using Bloom:

(Note that to get the indirect lighting on the sphere to work in Eevee you will need to add Light Probes and bake the lights.)