how do i make a grid like this in the video

• Start with a Gray 3D solid with the anchor point at the bottom center of the layer. 
• Adding Fractal noise will give you a wide range of luminance values that you can animate if you want
• Mosaic will give you a pattern of squares with the brightness depending on the color values in the grid
• Grid with the Blend mode set to Stencil Alpha will create a transparent grid
• Invert set to Alpha will give you the solid rectangles with transparency
• Curves will let you control the intensity of the contrast in the grid

• Put  some suitable footage below the grid and make it 3D
• Parent the footage layer to the grid layer above
• Experiment with Blend Modes - for this comp Linear Light looks like a good fit for the design
• Experiment with Curves, Blurs, Glows and other distortion effects to polish the look
• Animate the Y rotation of the grid layer to make the grid fall back

Here's is everything that I did to both layers in my example.

That is only one of about 10 ways that I can think of to recreate the effect. It's all about layering. The other mosaic transitions could be created using similar techniques, then the two comps could be combined in a master comp to transition from one effect to the next. I would not do both in one comp.

I added a time*360 expression to the fractal noise evolution to get the grid to animate then rendered a preview. This is what the animation looks like:

It's even better with sound...

This will get you started.

...anything from manually arranging a ton of solids to creating a shape layer array with the repeater to using effects like Card Dance. Entirely depends on what kind of animation you plan on doing.

Mylenium