diff --git a/lighthouse/main.rs b/lighthouse/main.rs
index 603346b36d..0b678fa468 100644
--- a/lighthouse/main.rs
+++ b/lighthouse/main.rs
@@ -8,11 +8,16 @@ extern crate network_libp2p;
 extern crate futures;
 
 #[macro_use]
+#[allow(dead_code)]
 mod utils;
+#[allow(dead_code)]
 mod bls;
+#[allow(dead_code)]
 mod db;
 mod client;
+#[allow(dead_code)]
 mod state;
+#[allow(dead_code)]
 mod sync;
 mod config;
 
diff --git a/lighthouse/state/attestation_record/mod.rs b/lighthouse/state/attestation_record/mod.rs
index d96a451fdd..447bb53829 100644
--- a/lighthouse/state/attestation_record/mod.rs
+++ b/lighthouse/state/attestation_record/mod.rs
@@ -1,10 +1,13 @@
 use super::bls;
+use super::common;
+use super::db;
 use super::ssz;
 use super::utils;
 
 
 mod attestation_record;
 mod ssz_splitter;
+pub mod validation;
 
 pub use self::attestation_record::{
     AttestationRecord,
diff --git a/lighthouse/state/validation/attestation/attestation_validation.rs b/lighthouse/state/attestation_record/validation/attestation_validation.rs
similarity index 100%
rename from lighthouse/state/validation/attestation/attestation_validation.rs
rename to lighthouse/state/attestation_record/validation/attestation_validation.rs
index 4822851250..0d20bb466c 100644
--- a/lighthouse/state/validation/attestation/attestation_validation.rs
+++ b/lighthouse/state/attestation_record/validation/attestation_validation.rs
@@ -1,10 +1,10 @@
 use std::collections::HashSet;
 use super::attestation_record::AttestationRecord;
+use super::AttesterMap;
 use super::attestation_parent_hashes::{
     attestation_parent_hashes,
     ParentHashesError,
 };
-use super::AttesterMap;
 use super::db::{
     ClientDB,
     DBError
diff --git a/lighthouse/state/validation/attestation/mod.rs b/lighthouse/state/attestation_record/validation/mod.rs
similarity index 74%
rename from lighthouse/state/validation/attestation/mod.rs
rename to lighthouse/state/attestation_record/validation/mod.rs
index a28f3c6acc..388685b60b 100644
--- a/lighthouse/state/validation/attestation/mod.rs
+++ b/lighthouse/state/attestation_record/validation/mod.rs
@@ -1,9 +1,9 @@
-use super::AttesterMap;
+use super::common::maps::AttesterMap;
 use super::db;
 use super::bls;
 use super::attestation_record;
 use super::ssz;
-use super::attestation_parent_hashes;
+use super::common::attestation_parent_hashes;
 use super::utils;
 
 mod attestation_validation;
diff --git a/lighthouse/state/validation/attestation/signatures.rs b/lighthouse/state/attestation_record/validation/signatures.rs
similarity index 100%
rename from lighthouse/state/validation/attestation/signatures.rs
rename to lighthouse/state/attestation_record/validation/signatures.rs
diff --git a/lighthouse/state/block/mod.rs b/lighthouse/state/block/mod.rs
index 20467eca7f..6838b2a48c 100644
--- a/lighthouse/state/block/mod.rs
+++ b/lighthouse/state/block/mod.rs
@@ -1,11 +1,15 @@
 extern crate blake2_rfc;
 
+use super::common;
+use super::Logger;
+use super::db;
 use super::ssz;
 use super::utils;
 use super::attestation_record;
 
 mod block;
 mod ssz_block;
+mod validation;
 
 pub use self::block::Block;
 pub use self::ssz_block::SszBlock;
diff --git a/lighthouse/state/block/validation/mod.rs b/lighthouse/state/block/validation/mod.rs
new file mode 100644
index 0000000000..ea4462ea1e
--- /dev/null
+++ b/lighthouse/state/block/validation/mod.rs
@@ -0,0 +1,17 @@
+mod validate_ssz_block;
+
+use super::attestation_record;
+use super::SszBlock;
+use super::Logger;
+use super::db;
+use super::ssz;
+use super::utils;
+
+use super::common::maps::{
+    AttesterMap,
+    ProposerMap,
+};
+pub use self::validate_ssz_block::{
+    validate_ssz_block,
+    SszBlockValidationError
+};
diff --git a/lighthouse/state/validation/ssz_block.rs b/lighthouse/state/block/validation/validate_ssz_block.rs
similarity index 99%
rename from lighthouse/state/validation/ssz_block.rs
rename to lighthouse/state/block/validation/validate_ssz_block.rs
index 90c2e22618..0a62c7f678 100644
--- a/lighthouse/state/validation/ssz_block.rs
+++ b/lighthouse/state/block/validation/validate_ssz_block.rs
@@ -1,5 +1,5 @@
 use std::sync::Arc;
-use super::attestation::{
+use super::attestation_record::validation::{
     validate_attestation,
     AttestationValidationError,
 };
@@ -13,7 +13,7 @@ use super::{
     AttesterMap,
     ProposerMap,
 };
-use super::block::SszBlock;
+use super::SszBlock;
 use super::db::{
     ClientDB,
     DBError,
diff --git a/lighthouse/state/transition/attestation_parent_hashes.rs b/lighthouse/state/common/attestation_parent_hashes.rs
similarity index 100%
rename from lighthouse/state/transition/attestation_parent_hashes.rs
rename to lighthouse/state/common/attestation_parent_hashes.rs
diff --git a/lighthouse/state/common/maps.rs b/lighthouse/state/common/maps.rs
new file mode 100644
index 0000000000..745f474c6a
--- /dev/null
+++ b/lighthouse/state/common/maps.rs
@@ -0,0 +1,7 @@
+use std::collections::HashMap;
+
+/// Maps a (slot, shard_id) to attestation_indices.
+pub type AttesterMap = HashMap<(u64, u64), Vec<usize>>;
+
+/// Maps a slot to a block proposer.
+pub type ProposerMap = HashMap<u64, usize>;
diff --git a/lighthouse/state/transition/mod.rs b/lighthouse/state/common/mod.rs
similarity index 89%
rename from lighthouse/state/transition/mod.rs
rename to lighthouse/state/common/mod.rs
index 7510796716..96ff38eb95 100644
--- a/lighthouse/state/transition/mod.rs
+++ b/lighthouse/state/common/mod.rs
@@ -1,6 +1,7 @@
-use super::utils::types::Hash256;
-
-pub mod attestation_parent_hashes;
 mod shuffling;
 
+pub mod maps;
+pub mod attestation_parent_hashes;
+
+use super::utils::types::Hash256;
 pub use self::shuffling::shuffle;
diff --git a/lighthouse/state/transition/shuffling/README.md b/lighthouse/state/common/shuffling/README.md
similarity index 100%
rename from lighthouse/state/transition/shuffling/README.md
rename to lighthouse/state/common/shuffling/README.md
diff --git a/lighthouse/state/transition/shuffling/mod.rs b/lighthouse/state/common/shuffling/mod.rs
similarity index 100%
rename from lighthouse/state/transition/shuffling/mod.rs
rename to lighthouse/state/common/shuffling/mod.rs
diff --git a/lighthouse/state/transition/shuffling/rng.rs b/lighthouse/state/common/shuffling/rng.rs
similarity index 100%
rename from lighthouse/state/transition/shuffling/rng.rs
rename to lighthouse/state/common/shuffling/rng.rs
diff --git a/lighthouse/state/mod.rs b/lighthouse/state/mod.rs
index 532d8345dc..10d9a18468 100644
--- a/lighthouse/state/mod.rs
+++ b/lighthouse/state/mod.rs
@@ -4,10 +4,7 @@ extern crate blake2_rfc as blake2;
 extern crate bytes;
 extern crate ssz;
 
-use super::bls;
-use super::db;
-use super::Logger;
-use super::utils;
+mod common;
 
 pub mod active_state;
 pub mod attestation_record;
@@ -16,7 +13,10 @@ pub mod chain_config;
 pub mod block;
 pub mod crosslink_record;
 pub mod shard_and_committee;
-pub mod transition;
 pub mod validator_record;
-pub mod validation;
 pub mod helpers;
+
+use super::bls;
+use super::db;
+use super::Logger;
+use super::utils;
diff --git a/lighthouse/state/validation/mod.rs b/lighthouse/state/validation/mod.rs
deleted file mode 100644
index 8ad367f4ab..0000000000
--- a/lighthouse/state/validation/mod.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-use std::collections::HashMap;
-use super::block;
-use super::bls;
-use super::Logger;
-use super::db;
-use super::attestation_record;
-use super::ssz;
-use super::transition::attestation_parent_hashes;
-use super::utils;
-
-mod attestation;
-mod ssz_block;
-
-type Slot = u64;
-type ShardId = u64;
-type AttesterMap = HashMap<(Slot, ShardId), Vec<usize>>;
-type ProposerMap = HashMap<Slot, usize>;
diff --git a/lighthouse/sync/block.rs b/lighthouse/sync/block.rs
new file mode 100644
index 0000000000..e69de29bb2