diff --git a/src/body.jl b/src/body.jl
deleted file mode 100644
index 1a303e5..0000000
--- a/src/body.jl
+++ /dev/null
@@ -1,76 +0,0 @@
-module body
-
-# TODO: Why do this?
-import Base.show
-
-export DefinitionHeader, DataRecord, read_row
-
-include("bytes.jl"); using.bytes
-include("mesg_num.jl"); using .mesg_num
-
-
-struct DefinitionHeader
-    endianness::AbstractString
-    number::Int64
-    fields::UInt8 
-end
-
-# TODO: field_number has a string value, type has a Julia type.
-struct DefinitionField
-    field_number::AbstractString
-    size::UInt8
-    type::UInt8
-end
-
-struct DataRecord
-    hdr::DefinitionHeader
-end
-
-
-"""
-    read_row(f::io)
-
-Read a row of the file at a time. Parse the row into a data or def message.
-TODO: Endianness matters here. Need to resolve endianness with the architecture bit.
-"""
-function read_row(f::IO)::DefinitionHeader
-    header_byte = read(f, 1; all=false)[1]
-
-    definition_message = Bool(bit_at(header_byte, 2))
-    # The message byte is 7
-    # hdr = RecordHeader(
-    #     Bool(bit_at(header_byte, 2)),
-    #     Bool(bit_at(header_byte, 1)))
-    # TODO: hdr if compressed timestamp needs to be handled in special way.
-    
-    if definition_message
-        fixed_bytes = read(f, 5; all=false)
-        hdr = DefinitionHeader(
-            endianness(fixed_bytes[2]), byte_vec_to_int(fixed_bytes[3:4]), fixed_bytes[end] 
-        )
-    end
-    hdr_fields = [hdr_field(read(f, 3; all=false)) for i ∈ 1:hdr.fields + 1]
-    println(hdr_fields)
-    hdr
-end
-
-function hdr_field(vec::Vector{UInt8})::DefinitionField
-    println(vec)
-    DefinitionField(
-        get_mesg_num_string(vec[1]), vec[2], vec[3]
-    )
-end
-
-function endianness(b::UInt8)::AbstractString
-    Bool(b) ? "BigEndian" : "LittleEndian"
-end
-
-function show(io::IO, header::DefinitionHeader)
-    print(io, "DefinitionHeader($(header.endianness), $(header.number), $(header.fields) messages)")
-end
-
-function show(io::IO, field::DefinitionField)
-    print(io, "DefinitionField($(field.field_number), $(field.size), $(field.type))")
-end
-
-end
diff --git a/src/bytes.jl b/src/bytes.jl
index 95073aa..4c2f27c 100644
--- a/src/bytes.jl
+++ b/src/bytes.jl
@@ -1,6 +1,6 @@
 module bytes
 
-export byte_vec_to_int, byte_vec_to_string, bit_at
+export byte_vec_to_int, byte_vec_to_string, bit_at, bit_vector
 
 """
     read_data_size(size::Vector{UInt8})::Real
@@ -36,4 +36,21 @@ function bit_at(byte::UInt8, idx::Int64; t::Type=Int64)::Int64
 end
 
 end
-# byte_vec_to_string(UInt8.(collect("ABC")))
\ No newline at end of file
+# byte_vec_to_string(UInt8.(collect("ABC")))
+
+function bit_vector(byte::UInt8; little_endian=false)::Vector{UInt8}
+    range = if little_endian
+        8:-1:1
+    else
+        1:1:8
+    end
+
+    s = bitstring(byte)
+    [parse(UInt8, s[b]) for b in range]
+end
+
+
+function bit_vector(byte_vector::Vector{UInt8}; little_endian=false)::Vector{UInt8}
+    vecs = [bit_vector(byte; little_endian=little_endian) for byte ∈ byte_vector]
+    reduce(vcat, vecs)
+end
\ No newline at end of file
diff --git a/src/file.jl b/src/file.jl
index 1555a46..cbf583a 100644
--- a/src/file.jl
+++ b/src/file.jl
@@ -2,7 +2,6 @@ module file
 
 export FITFile, read_file
 
-include("body.jl"); using .body
 include("bytes.jl"); using .bytes
 
 
@@ -17,16 +16,22 @@ struct FITHeader
     crc::AbstractVector{<:Real}
 end
 
+mutable struct DataRecord
+    definition::Bool
+    data::Bool
+end
+
 mutable struct FITFileReader
     filepath::AbstractString
     fp::Union{IO, Nothing}
     bytes_read::Int64
     header::Union{FITHeader, Nothing}
-    body::Union{DefinitionHeader, Nothing}
+    body::Union{Vector{DataRecord}, Nothing}
 end
 
 
 blank_file(fp::AbstractString) = FITFileReader(fp, nothing, 0, nothing, nothing)
+blank_row() = DataRecord(false, false)
 
 """
     open_fit_file!(f::FITFileReader)
@@ -47,6 +52,16 @@ function close_fit_file!(f::FITFileReader)
     f.fp = nothing
 end
 
+"""
+    read_bytes!(f::FITFileReader, nb::Integer)::Vector{UInt8}
+
+Read nb bytes from f, update f.bytes_read, return bytes
+"""
+function read_bytes!(f::FITFileReader, nb::Integer)::Vector{UInt8}
+    bytes = read(f.fp, nb; all=false)
+    f.bytes_read += max(length(bytes), nb)
+    bytes
+end
 
 """
     read_header(fit_file::IOStream)
@@ -54,7 +69,7 @@ end
 Read the header of the given fit file, and return a FITHeader struct
 """
 function read_header!(f::FITFileReader)
-    header = read(f.fp, HEADER_SZ; all=false)
+    header = read_bytes!(f, HEADER_SZ)
     f.header = FITHeader(
         header[1],
         header[2],
@@ -63,7 +78,42 @@ function read_header!(f::FITFileReader)
         byte_vec_to_string(header[9:12]),
         header[13:14]
     )
-    f.bytes_read += HEADER_SZ
+end
+
+"""
+    decode_header(v::Vector{UInt8})
+
+Decode the header byte, determine if the record is a definition, data, or timestamp.
+"""
+function decode_header(v::Vector{UInt8})::DataRecord
+    record = blank_row()
+
+    record.definition = v[7] === 0x01
+    record.data = !record.definition
+end
+
+"""
+    read_records!(f::FITFileReader)
+
+Read all the data record messages.
+"""
+function read_records!(f::FITFileReader)
+    if f.bytes_read < 12 || f.bytes_read > 14
+        throw("invalid header read, not within header size")
+    end
+
+    # Read header byte - decode
+    header_bits = bit_vector(read_bytes!(f, 1); little_endian=true)
+    record = decode_header(header_bits)
+
+    # Push record to the body.
+    if isnothing(f.body)
+        f.body = [record]
+    else
+        push!(f.body, record)
+    end
+
+    record
 end
 
 function read_file(filepath::AbstractString)::FITFileReader
@@ -71,7 +121,9 @@ function read_file(filepath::AbstractString)::FITFileReader
 
     open_fit_file!(f)
     try
-        read_header!(f) 
+        read_header!(f)
+        read_records!(f)
+        # read_rows!(f)
     catch e
         rethrow(e)
     finally