custom struct not showing up in inspector?

I’m trying to cluster data into better handleable chunks. I’m experimenting with classes and Javascript structs (as described here). My custom structs are not showing up in the inspector even though similarly coded classes do! I can access/edit them from a script just fine but tracking them in the inspector or even setting their values is not possible. What’s wrong wit my implementation?

#pragma strict

var dummy1 : Vector3; // shows up
var dummy2 : TestStruct; // does not show up
var dummy3 : TestClass; // shows up
var dummy4 : Vector3; // shows up

function Start () {
	dummy2.t=2;
	dummy3.t=3;
	print(dummy2);
	print(dummy2.t);
	print(dummy3);
	print(dummy3.t);
}

class TestStruct extends System.ValueType{
	var x : float;
	var y : float;
	var z : float;
	var t : float;
}
class TestClass {
	var x : float;
	var y : float;
	var z : float;
	var t : float;
}

Serializing structs in Unity is actually possible now. I found this on the forums (1):

    [System.Serializable]
    public struct PlayerStats
    {
        public int moveSpeed;
    }

I have tried it and it works fine.

Update
Unity now supports the serialization of structs, so the old answer does no longer apply to the current versions of Unity. No need to downvote ancient answers that were perfectly valid when they were posted 10 years ago.

I’m afraid this can’t be done on Unity. Classes will do fine but structs can’t be serialized with Unity and thus, won’t display on the inspector. I don’t know the reasons for this limitation (I think it’s fair to call it a limitation) but I bet this is because of structs being value types, not refference ones, but as floats and integers can be assigned, there might be something else there…

Anyway, you might want to check this out: http://forum.unity3d.com/threads/36395-How-do-I-make-member-structs-accessible-in-the-editor?highlight=struct+inspector